GIS DataTypes in SQL Server 2008

Microsoft's SQL Server 2008 offers new support for spatial data types that some analysts say should deliver a real boost to geospatial applications and data sharing.

Expected to ship in the third quarter, the new version of SQL Server will allow storage of spatial data -- in the form of points, lines and polygons -- in SQL tables. The software will also offer a set of functions to allow the manipulation of this data and new spatial indexes to support the execution of these functions.

What is GIS?

geographic information system (GIS) integrates hardware, software, and data for capturing, managing, analyzing, and displaying all forms of geographically referenced information.

Why GIS?

GIS allows us to view, understand, question, interpret, and visualize data in many ways that reveal relationships, patterns, and trends in the form of maps, globes, reports, and charts.

A GIS helps you answer questions and solve problems by looking at your data in a way that is quickly understood and easily shared.

GIS technology can be integrated into any enterprise information system framework.

A GIS can be viewed in three ways:

1. The Database View

2. The Map View

3. The model View

XP_cmdshell extended stored procedure (Execute Winows commands)

xp_cmdshell

Executes a given command string or batch file as an operating-system command shell and returns any output as rows of text.

Permission/Rights: Only SysAdmin fixed role can execute it.

Syntax

xp_cmdshell {'command_string'} [, no_output]

Arguments

'command_string'

Is the command string to execute at the operating-system command shell or from DOS prompt. command_string is varchar(255) or nvarchar(4000), with no default.

command_string cannot contain more than one set of double quotation marks.

A single pair of quotation marks is necessary if any spaces are present in the file paths or program names referenced by command_string.

If you have trouble with embedded spaces, consider using FAT 8.3 file names as a workaround.

no_output

Is an optional parameter executing the given command_string, and does not return any output to the client.

Examples
xp_cmdshell 'dir *.jpg'

Executing this xp_cmdshell statement returns the following result set:

xp_cmdshell 'dir *.exe', NO_OUTPUT

Here is the result:

The command(s) completed successfully.

<!--[if gte vml 1]&gt; &lt;![endif]--><!--[if !vml]--><!--[endif]-->

Examples

Copy File
EXEC xp_cmdshell 'copy c:\sqldumps\jshah143.bak \\server2\backups\jshah143.bak',  NO_OUTPUT

 

Use return status

In this example, the xp_cmdshell extended stored procedure also suggests return status. The return code value is stored in the variable @result.

DECLARE @result int
EXEC @result = xp_cmdshell 'dir *.exe'
IF (@result = 0)
   PRINT 'Success'
ELSE
   PRINT 'Failure'

 

Pass the parameter to batch file

DECLARE @sourcepath VARCHAR(100)
DECLARE @destinationpath VARCHAR(1000)
SET @sourcepath = ' c:\sqldumps\jshah143.bak '
SET @destinationpath = '\\server2\backups\jshah143.bak'
 
SET @CMDSQL = 'c:copyfile.bat' + @sourcepath + @destinationpath
EXEC master..XP_CMDShell @CMDSQL

How to read transaction log data in SQL Server 2000/2005?

 

We can't read the transaction logs directly from SQL Server. Some products do allow you to read the logs, such as:

* Apex SQL Log (Works with MSSQL2000 and MSSQL2005)
* Log Explorer
* SQL Log Rescue (Only work with the SQL Server 2000)

The below undocumented DBCC command is working in both SQL Server 2000 & SQL Server 2005

DBCC LOG(<database name>[,{0|1|2|3|4}])
0 - Basic Log Information (default)
1 - Lengthy Info
2 - Very Length Info
3 - Detailed
4 - Full Example
Syntax:
DBCC log (MY_DB, 4)

Another undocumented command is DBCC LOGINFO

Disk Space Alerts using SQL Server 2005

Please visit http://sqldbpool.blogspot.com/

Step 1: Create the database mail profile account using SQL Server Management Studio. Give the profile name to "FreeSpaceAlertMails"

Step2: Create the below procedure in master database which will check the disk space.

CREATE PROCEDURE sendAlertMails
AS
BEGIN
SET NOCOUNT ON
DECLARE @availableSpace AS FLOAT
DECLARE @alertMessage AS Varchar(4000)

CREATE TABLE #tbldiskSpace
(
driveName VARCHAR(3),
freeSpace FLOAT
)

INSERT INTO #tbldiskSpace EXEC master..XP_FixedDrives
SELECT @availableSpace = ROUND((freeSpace)/1024,1) FROM #tbldiskSpace WHERE driveName = 'E'

SET @alertMessage = '(host:jshah.sqldbpool.com)E:\ Disk Space Critical. Free Space Available on E:\ Drive is ' + CAST(@availableSpace AS VARCHAR) + 'GB'

IF @availableSpace < 10
BEGIN
EXEC msdb.dbo.sp_send_dbmail
@profile_name = 'FreeSpaceAlertMails',
@recipients = 'jshah143@gmail.com',
@body = @alertMessage,
@importance = 'High',
@subject = 'host:jshah.sqldbpool.com Disk Critical E Drive' ;
END

DROP TABLE #tbldiskSpace

END

Step 3: Create the job which will execute the above procedure at every 2 hours interval.

DOS Commands for DBA

As SQL Server DBA, there are many activities which needs the knowledge of DOS Commands. Please find the below useful DOS Commands.

ANSI.SYS - Defines functions that change display graphics, control cursor movement, and reassign keys.
APPEND - Causes MS-DOS to look in other directories when editing a file or running a command.
ARP - Displays, adds, and removes arp information from network devices.
ASSIGN - Assign a drive letter to an alternate letter.
ASSOC - View the file associations.
AT - Schedule a time to execute commands or programs.
ATMADM - Lists connections and addresses seen by Windows ATM call manager.
ATTRIB - Display and change file attributes.
BATCH - Recovery console command that executes a series of commands in a file.
BOOTCFG - Recovery console command that allows a user to view, modify, and rebuild the boot.ini
BREAK - Enable / disable CTRL + C feature.
CACLS - View and modify file ACL's.
CALL - Calls a batch file from another batch file.
CD - Changes directories.
CHCP - Supplement the International keyboard and character set information.
CHDIR - Changes directories.
CHKDSK - Check the hard disk drive running FAT for errors.
CHKNTFS - Check the hard disk drive running NTFS for errors.
CHOICE - Specify a listing of multiple options within a batch file.
CLS - Clears the screen.
CMD - Opens the command interpreter.
COLOR - Easily change the foreground and background color of the MS-DOS window.
COMMAND - Opens the command interpreter.
COMP - Compares files.
COMPACT - Compresses and uncompress files.
CONTROL - Open control panel icons from the MS-DOS prompt.
CONVERT - Convert FAT to NTFS.
COPY - Copy one or more files to an alternate location.
CTTY - Change the computers input/output devices.
DATE - View or change the systems date.
DEBUG - Debug utility to create assembly programs to modify hardware settings.
DEFRAG - Re-arrange the hard disk drive to help with loading programs.
DEL - Deletes one or more files.
DELETE - Recovery console command that deletes a file.
DELTREE - Deletes one or more files and/or directories.
DIR - List the contents of one or more directory.
DISABLE - Recovery console command that disables Windows system services or drivers.
DISKCOMP - Compare a disk with another disk.
DISKCOPY - Copy the contents of one disk and place them on another disk.
DOSKEY - Command to view and execute commands that have been run in the past.
DOSSHELL - A GUI to help with early MS-DOS users.
DRIVPARM - Enables overwrite of original device drivers.
ECHO - Displays messages and enables and disables echo.
EDIT - View and edit files.
EDLIN - View and edit files.
EMM386 - Load extended Memory Manager.
ENABLE - Recovery console command to enable a disable service or driver.
ENDLOCAL - Stops the localization of the environment changes enabled by the setlocal command.
ERASE - Erase files from computer.
EXIT - Exit from the command interpreter.
EXPAND - Expand a Microsoft Windows file back to it's original format.
EXTRACT - Extract files from the Microsoft Windows cabinets.
FASTHELP - Displays a listing of MS-DOS commands and information about them.
FC - Compare files.
FDISK - Utility used to create partitions on the hard disk drive.
FIND - Search for text within a file.
FINDSTR - Searches for a string of text within a file.
FIXBOOT - Writes a new boot sector.
FIXMBR - Writes a new boot record to a disk drive.
FORMAT - Command to erase and prepare a disk drive.
FTP - Command to connect and operate on a FTP server.
FTYPE - Displays or modifies file types used in file extension associations.
GOTO - Moves a batch file to a specific label or location.
GRAFTABL - Show extended characters in graphics mode.
HELP - Display a listing of commands and brief explanation.
IF - Allows for batch files to perform conditional processing.
IFSHLP.SYS - 32-bit file manager.
IPCONFIG - Network command to view network adapter settings and assigned values.
KEYB - Change layout of keyboard.
LABEL - Change the label of a disk drive.
LH - Load a device driver in to high memory.
LISTSVC - Recovery console command that displays the services and drivers.
LOADFIX - Load a program above the first 64k.
LOADHIGH - Load a device driver in to high memory.
LOCK - Lock the hard disk drive.
LOGON - Recovery console command to list installations and enable administrator login.
MAP - Displays the device name of a drive.
MD - Command to create a new directory.
MEM - Display memory on system.
MKDIR - Command to create a new directory.
MODE - Modify the port or display settings.
MORE - Display one page at a time.
MOVE - Move one or more files from one directory to another directory.
MSAV - Early Microsoft Virus scanner.
MSD - Diagnostics utility.
MSCDEX - Utility used to load and provide access to the CD-ROM.
NBTSTAT - Displays protocol statistics and current TCP/IP connections using
NET - Update, fix, or view the network or network settings
NETSH - Configure dynamic and static network information from MS-DOS.
NETSTAT - Display the TCP/IP network protocol statistics and information.
NLSFUNC - Load country specific information.
NSLOOKUP - Look up an IP address of a domain or host on a network.
PATH - View and modify the computers path location.
PATHPING - View and locate locations of network latency.
PAUSE - Command used in batch files to stop the processing of a command.
PING - Test / send information to another network computer or network device.
POPD - Changes to the directory or network path stored by the pushd command.
POWER - Conserve power with computer portables.
PRINT - Prints data to a printer port.
PROMPT - View and change the MS-DOS prompt.
PUSHD - Stores a directory or network path in memory so it can be returned to at any time.
QBASIC - Open the QBasic.
RD - Removes an empty directory.
REN - Renames a file or directory.
RENAME - Renames a file or directory.
RMDIR - Removes an empty directory.
ROUTE - View and configure windows network route tables.
RUNAS - Enables a user to execute a program on another computer.
SCANDISK - Run the scandisk utility.
SCANREG - Scan registry and recover registry from errors.
SET - Change one variable or string to another.
SETLOCAL - Enables local environments to be changed without affecting anything else.
SETVER - Change MS-DOS version to trick older MS-DOS programs.
SHARE - Installs support for file sharing and locking capabilities.
SHIFT - Changes the position of replaceable parameters in a batch program.
SHUTDOWN - Shutdown the computer from the MS-DOS prompt.
SMARTDRV - Create a disk cache in conventional memory or extended memory.
SORT - Sorts the input and displays the output to the screen.
START - Start a separate window in Windows from the MS-DOS prompt.
SUBST - Substitute a folder on your computer for another drive letter.
SWITCHES - Remove add functions from MS-DOS.
SYS - Transfer system files to disk drive.
TELNET - Telnet to another computer / device from the prompt.
TIME - View or modify the system time.
TITLE - Change the title of their MS-DOS window.
TRACERT - Visually view a network packets route across a network.
TREE - View a visual tree of the hard disk drive.
TYPE - Display the contents of a file.
UNDELETE - Undelete a file that has been deleted.
UNFORMAT - Unformat a hard disk drive.
UNLOCK - Unlock a disk drive.
VER - Display the version information.
VERIFY - Enables or disables the feature to determine if files have been written properly.
VOL - Displays the volume information about the designated drive.
XCOPY - Copy multiple files, directories, and/or drives from one location to another.

SQL Server 2000 Query Analyzer Shortcut

Shortcut	Function		Shortcut	Function
ALT+BREAK	Cancel a query		CTRL+SHIFT+F2	Clear all bookmarks
ALT+F1	Database object information (Sp_Help)		CTRL+SHIFT+INSERT	Insert a template
ALT+F4	Exit		CTRL+SHIFT+L	Make selection lowercase
ISQLW	To start query analyzer from RUN window		CTRL+SHIFT+M	Replace template parameters
CTRL+B	Move the splitter		CTRL+SHIFT+P	Open
SQLWb	To start management studio from command window		CTRL+SHIFT+R	Remove comment
CTRL+D	Display results in grid format		CTRL+SHIFT+S	Show client statistics
CTRL+Delete	Delete through the end of the line		CTRL+SHIFT+T	Show server trace
CTRL+E	Execute query		CTRL+SHIFT+U	Make selection uppercase
CTRL+F	Find		CTRL+T	Display results in text format
CTRL+F2	Insert/remove bookmark		CTRL+U	Change database
CTRL+F4	Disconnect		CTRL+V	Paste
CTRL+F5	Parse query and check syntax		CTRL+W	Window selector
CTRL+G	Go to line		CTRL+X	Delete
CTRL+H	Replace		CTRL+Z	Undo
CTRL+I	Index Tuning Wizard		F1	Help for Query Analyzer
CTRL+K	Display/hide execution plan		F2	Move to next bookmark
CTRL+L	Display execution plan		F3	Repeat last search
CTRL+N	New query window		F4	Object Search
CTRL+O	Connect		F5	Execute a query
CTRL+P	Print		F6	Switch between query and result panes
CTRL+R	Show/Hide results pane		F8	Show/hide Object Browser
CTRL+S	Save		SHIFT+F1	Transact-SQL help
CTRL+SHIFT+0	Show options		SHIFT+F2	Move to previous bookmark
CTRL+SHIFT+C	Comment out code		SHIFT+TAB	Decrease indent
CTRL+SHIFT+DEL	Clear the active Editor pane		SHIFT+F6	Switch panes
CTRL+SHIFT+F	Save results to file		TAB	Increase indent

SQL Server 2005 Questions and Answers

Q. What is CTE (Common Table Expression)?
Ans: CTE is a temporary Table created from a simple SQL query. You can say it's a view. Below is a sample CTE created "PurchaseOrderHeaderCTE" from "PurchaseOrderHearder"

With PurchaseOrderHeaderCTE (Orderdate, status) As
(
SELECT order date, status
FROM Purchasing.PurchasingOrderheader

)

SELECT * FROM PurchasingOrderheader

The WITH Statement define the CTE and later using the CTE name I have display the CTE data.

Q. Why would you use CTE rather than simple View?
With CTE you can use a recursive query with CTE itself. That's not possible with view.

Q. What is TRY/CATCH block in T-SQL?
NO I am referring to .NET TRY/CATCH block, this is a new way of handling error in SQL Server. For instance in the below T-SQL code any error during delete statement is caugh and the neccessary error information is displayed:

BEGIN TRY
DELETE table 1 WHERE id=122
END TRY

BEGIN CATCH
SELECT
ERROR_NUMBER As ErrNum,
ERROR_SEVERITY ( ) As ErrSev,
ERROR_STATE ( ) As ErrSt,
ERROR_MESSAGE ( ) As ErrMsg;
END CATCH

Q. What is PIVOT feature in SQL Server?
PIVOT feature convert data row to column for better analytical view. Below is a sample PIVOT filed using CTE. OK the first section is the CTE which is the input and later PIVOT is applied Over it:

WITH PURCHASEORDERHEADERCTE(Orderdate, Status, Subtotal) As
(

select year (orderdate), status, isnull(SubTotal, 0) from purchasing. PURCHASEORDER HEADER

)

Select Status as OrderStatus, isnull ([2006], 0 ) as 'YR 2007', isnull([2007], 0) as 'Yr 2007' from PURCHASEORDERHEADERCTE Pivot (sum(subtotal) for Orderdate in ([2006], [2007] ) ) as pivoted
You can see from the above SQL the top WITH statement is the CTE supplied to the PIVOT. After that PIVOT is applied on subtotal and orderdate. You have to secify in what you want the pivot (here it is 2006 and 2007). So below is the output of CTE table.

(No column name) Status (No column Name)
1 2006 4 201.4
2 2006 1 272.1015
3 2006 4 8847.30
4 2006 3 171.0765
5 2006 4 20397.30
6 2006 4 14628.075
7 2006 4 58685.55
8 2006 4 693.378
9 2007 4 694.1655
10 2007 4 1796.0355
11 2007 4 501.1965

CTE ouput
After the PIVOT is applied you can see the rows now grouped column wise with the subtotal assigned to each. You can summarize that PIVOT summarizies your data in cross tab format.

Order Status Yr 2006 Yr 2007
1 3 171.0765 383552.904
2 1 272.1015 0.00
3 4 103452.643 3842580.126

Q. What is UNPIVOT?
It's exactly the vice versa of PIVOT. That means you have a PIVOTED data and you want to UNPIVOTED.

Q. What are RANKING functions?
they add columns that are calculated based on a ranking algorithm. These functions include ROW_NUMBER( ), RANK( ), DENSE_RANK(), and NTILE().

Q. What is ROW_NUMBER()?
The ROW_NUMER() function adds a column that display a number corresponding the row's position is the query result. If the column that you specify in the OVER clause is not unique, it still produces an incrementing column based on the column specified in the OVER Clause. YOu can see in the figure below I have applied ROW_NUMBER function over column col2 and you notive the incrementing numbers generated.

Select col1, col2,
row_number(), over (order by col2) as ROW_NUMER from table _1

col1 col2 RowNumber
1 1 2 1
2 2 3 2
3 4 3 3
4 4 3 4
5 5 6 5
6 5 6 6

Q. What is RANK()?
The Rank() function works much like ROW_NUM() function in that is numbers records in order. When the column specified by the ORDER BY clause contains unique values, then ROW_NUMBER() and RANK() produce identical results. They differ in the way they work when duplicate values are contained in the ORDER BY expression. ROW_NUMBER will increment the number by one every record. regardless of duplicates. RANK() produces a single number for each value in the result set. You can see duplicate value it does not increment the TOP number.

Select col1, col2, RANK(), over (order by col2) as ROW_NUMER from table _1

col1 col2 ROW NUMBER
1 2 1
2 3 2
4 3 3
4 3 4
5 6 5

Q. What is DENSE_RANK()
DENSE_:RANK() works the same way as RANK() does but eliminates the gaps in thr numbering. When I say GAPS you can see in previous results it has eliminated 4 and 5 from the count because of the gap in between COL@. BUT for dense_rank it overlooks the gap.

Select col1, col2, Dense_rank(), over (order by col2) as ROW_NUMER from table _1
col1 col2 RowNumber
1 2 1
2 3 2
4 3 2
4 3 2
5 6 3
5 6 3

Q. What is NTILE()?
NTILES() breaks the result set into a specified number of groups and assigns the same number to each record in a group. OK NTILE just groups depending on the number given or you can say devide the data. For instance I have said to NTILE it to 3. It has 6 total rows so it grouped in number of 2.

Select col1, col2,NTILE(3) over (order by col2) as ROW_NUMER from table _1

col1 col2 RowNumber
1 2 1
2 3 1
4 3 2
4 3 2
5 6 3
5 6 3

Q. (DB) What is SQL Injection?
It is a form of attack on a database -driven Web site in which the attacker executes unauthorized SQL Commands by taking advance of insecute code on a system connected to the Internet. by passing the firewall. SQL injection attacks are used to steal information from the database from which the data would normally not be avaiable and gain access to an organization's host computers through the computer that is hosting the database.

SQL injection attacks typically are easy to avoid by ensuring that a system has strong input validation.
As name suggest's we inject SQL which can be relatively dangerous for the database. Exammple:

SELECT Email, passwd, login_id, Full_name
FROM Member
WHERE email = 'X'

Now some body does not put "x" as the input but put "x; DROP TABLE members;". So the actual SQL will execute is:

SELECT Email, passwd, login_id, Full_name
FROM Member
WHERE email = 'X' ; DROP TABLE members

FAQs in SQL Server and Oracle

1. What is database?

A database is a logically coherent collection of data with some inherent meaning, representing some aspect of real world and which is designed, built and populated with data for a specific purpose.

2. What is DBMS?
It is a collection of programs that enables user to create and maintain a database. In other words it is general-purpose software that provides the users with the processes of defining, constructing and manipulating the database for various applications.

3. What is a Database system?
The database and DBMS software together is called as Database system.

4. Advantages of DBMS?
Ø Redundancy is controlled.
Ø Unauthorised access is restricted.
Ø Providing multiple user interfaces.
Ø Enforcing integrity constraints.
Ø Providing backup and recovery.

5. Disadvantage in File Processing System?
Ø Data redundancy & inconsistency.
Ø Difficult in accessing data.
Ø Data isolation.
Ø Data integrity.
Ø Concurrent access is not possible.
Ø Security Problems.

6. Describe the three levels of data abstraction?
The are three levels of abstraction:
Ø Physical level: The lowest level of abstraction describes how data are stored.
Ø Logical level: The next higher level of abstraction, describes what data are stored in database and what relationship among those data.
Ø View level: The highest level of abstraction describes only part of entire database.

7. Define the "integrity rules"
There are two Integrity rules.
Ø Entity Integrity: States that “Primary key cannot have NULL value”
Ø Referential Integrity: States that “Foreign Key can be either a NULL value or should be Primary Key value of other relation.

8. What is extension and intension?
Extension -
It is the number of tuples present in a table at any instance. This is time dependent.
Intension -
It is a constant value that gives the name, structure of table and the constraints laid on it.

9. What is System R? What are its two major subsystems?
System R was designed and developed over a period of 1974-79 at IBM San Jose Research Center. It is a prototype and its purpose was to demonstrate that it is possible to build a Relational System that can be used in a real life environment to solve real life problems, with performance at least comparable to that of existing system.
Its two subsystems are
Ø Research Storage
Ø System Relational Data System.

10. How is the data structure of System R different from the relational structure?
Unlike Relational systems in System R
Ø Domains are not supported
Ø Enforcement of candidate key uniqueness is optional
Ø Enforcement of entity integrity is optional
Ø Referential integrity is not enforced

11. What is Data Independence?
Data independence means that “the application is independent of the storage structure and access strategy of data”. In other words, The ability to modify the schema definition in one level should not affect the schema definition in the next higher level.
Two types of Data Independence:
Ø Physical Data Independence: Modification in physical level should not affect the logical level.
Ø Logical Data Independence: Modification in logical level should affect the view level.
NOTE: Logical Data Independence is more difficult to achieve

12. What is a view? How it is related to data independence?
A view may be thought of as a virtual table, that is, a table that does not really exist in its own right but is instead derived from one or more underlying base table. In other words, there is no stored file that direct represents the view instead a definition of view is stored in data dictionary.
Growth and restructuring of base tables is not reflected in views. Thus the view can insulate users from the effects of restructuring and growth in the database. Hence accounts for logical data independence.

13. What is Data Model?
A collection of conceptual tools for describing data, data relationships data semantics and constraints.

14. What is E-R model?
This data model is based on real world that consists of basic objects called entities and of relationship among these objects. Entities are described in a database by a set of attributes.

15. What is Object Oriented model?
This model is based on collection of objects. An object contains values stored in instance variables with in the object. An object also contains bodies of code that operate on the object. These bodies of code are called methods. Objects that contain same types of values and the same methods are grouped together into classes.

16. What is an Entity?
It is a 'thing' in the real world with an independent existence.

17. What is an Entity type?
It is a collection (set) of entities that have same attributes.

18. What is an Entity set?
It is a collection of all entities of particular entity type in the database.

19. What is an Extension of entity type?
The collections of entities of a particular entity type are grouped together into an entity set.

20. What is Weak Entity set?
An entity set may not have sufficient attributes to form a primary key, and its primary key compromises of its partial key and primary key of its parent entity, then it is said to be Weak Entity set.

21. What is an attribute?
It is a particular property, which describes the entity.

22. What is a Relation Schema and a Relation?
A relation Schema denoted by R(A1, A2, …, An) is made up of the relation name R and the list of attributes Ai that it contains. A relation is defined as a set of tuples. Let r be the relation which contains set tuples (t1, t2, t3, ..., tn). Each tuple is an ordered list of n-values t=(v1,v2, ..., vn).

23. What is degree of a Relation?
It is the number of attribute of its relation schema.

24. What is Relationship?
It is an association among two or more entities.

25. What is Relationship set?
The collection (or set) of similar relationships.

26. What is Relationship type?
Relationship type defines a set of associations or a relationship set among a given set of entity types.

27. What is degree of Relationship type?
It is the number of entity type participating.

25. What is DDL (Data Definition Language)?
A data base schema is specifies by a set of definitions expressed by a special language called DDL.

26. What is VDL (View Definition Language)?
It specifies user views and their mappings to the conceptual schema.

27. What is SDL (Storage Definition Language)?
This language is to specify the internal schema. This language may specify the mapping between two schemas.

28. What is Data Storage - Definition Language?
The storage structures and access methods used by database system are specified by a set of definition in a special type of DDL called data storage-definition language.

29. What is DML (Data Manipulation Language)?
This language that enable user to access or manipulate data as organised by appropriate data model.
Ø Procedural DML or Low level: DML requires a user to specify what data are needed and how to get those data.
Ø Non-Procedural DML or High level: DML requires a user to specify what data are needed without specifying how to get those data.

31. What is DML Compiler?
It translates DML statements in a query language into low-level instruction that the query evaluation engine can understand.

32. What is Query evaluation engine?
It executes low-level instruction generated by compiler.

33. What is DDL Interpreter?
It interprets DDL statements and record them in tables containing metadata.

34. What is Record-at-a-time?
The Low level or Procedural DML can specify and retrieve each record from a set of records. This retrieve of a record is said to be Record-at-a-time.

35. What is Set-at-a-time or Set-oriented?
The High level or Non-procedural DML can specify and retrieve many records in a single DML statement. This retrieve of a record is said to be Set-at-a-time or Set-oriented.

36. What is Relational Algebra?
It is procedural query language. It consists of a set of operations that take one or two relations as input and produce a new relation.

37. What is Relational Calculus?
It is an applied predicate calculus specifically tailored for relational databases proposed by E.F. Codd. E.g. of languages based on it are DSL ALPHA, QUEL.

38. How does Tuple-oriented relational calculus differ from domain-oriented relational calculus
The tuple-oriented calculus uses a tuple variables i.e., variable whose only permitted values are tuples of that relation. E.g. QUEL
The domain-oriented calculus has domain variables i.e., variables that range over the underlying domains instead of over relation. E.g. ILL, DEDUCE.

39. What is normalization?
It is a process of analysing the given relation schemas based on their Functional Dependencies (FDs) and primary key to achieve the properties
Ø Minimizing redundancy
Ø Minimizing insertion, deletion and update anomalies.

40. What is Functional Dependency?
A Functional dependency is denoted by X Y between two sets of attributes X and Y that are subsets of R specifies a constraint on the possible tuple that can form a relation state r of R. The constraint is for any two tuples t1 and t2 in r if t1[X] = t2[X] then they have t1[Y] = t2[Y]. This means the value of X component of a tuple uniquely determines the value of component Y.

41. When is a functional dependency F said to be minimal?
Ø Every dependency in F has a single attribute for its right hand side.
Ø We cannot replace any dependency X A in F with a dependency Y A where Y is a proper subset of X and still have a set of dependency that is equivalent to F.
Ø We cannot remove any dependency from F and still have set of dependency that is equivalent to F.

42. What is Multivalued dependency?
Multivalued dependency denoted by X Y specified on relation schema R, where X and Y are both subsets of R, specifies the following constraint on any relation r of R: if two tuples t1 and t2 exist in r such that t1[X] = t2[X] then t3 and t4 should also exist in r with the following properties
Ø t3[x] = t4[X] = t1[X] = t2[X]
Ø t3[Y] = t1[Y] and t4[Y] = t2[Y]
Ø t3[Z] = t2[Z] and t4[Z] = t1[Z]
where [Z = (R-(X U Y)) ]

43. What is Lossless join property?
It guarantees that the spurious tuple generation does not occur with respect to relation schemas after decomposition.

44. What is 1 NF (Normal Form)?
The domain of attribute must include only atomic (simple, indivisible) values.

45. What is Fully Functional dependency?
It is based on concept of full functional dependency. A functional dependency X Y is full functional dependency if removal of any attribute A from X means that the dependency does not hold any more.

46. What is 2NF?
A relation schema R is in 2NF if it is in 1NF and every non-prime attribute A in R is fully functionally dependent on primary key.

47. What is 3NF?
A relation schema R is in 3NF if it is in 2NF and for every FD X A either of the following is true
Ø X is a Super-key of R.
Ø A is a prime attribute of R.
In other words, if every non prime attribute is non-transitively dependent on primary key.

48. What is BCNF (Boyce-Codd Normal Form)?
A relation schema R is in BCNF if it is in 3NF and satisfies an additional constraint that for every FD X A, X must be a candidate key.

49. What is 4NF?
A relation schema R is said to be in 4NF if for every Multivalued dependency X Y that holds over R, one of following is true
Ø X is subset or equal to (or) XY = R.
Ø X is a super key.

50. What is 5NF?
A Relation schema R is said to be 5NF if for every join dependency {R1, R2, ..., Rn} that holds R, one the following is true
Ø Ri = R for some i.
Ø The join dependency is implied by the set of FD, over R in which the left side is key of R.

51. What is Domain-Key Normal Form?
A relation is said to be in DKNF if all constraints and dependencies that should hold on the the constraint can be enforced by simply enforcing the domain constraint and key constraint on the relation.

52. What are partial, alternate,, artificial, compound and natural key?
Partial Key:
It is a set of attributes that can uniquely identify weak entities and that are related to same owner entity. It is sometime called as Discriminator.
Alternate Key:
All Candidate Keys excluding the Primary Key are known as Alternate Keys.
Artificial Key:
If no obvious key, either stand alone or compound is available, then the last resort is to simply create a key, by assigning a unique number to each record or occurrence. Then this is known as developing an artificial key.
Compound Key:
If no single data element uniquely identifies occurrences within a construct, then combining multiple elements to create a unique identifier for the construct is known as creating a compound key.
Natural Key:
When one of the data elements stored within a construct is utilized as the primary key, then it is called the natural key.

53. What is indexing and what are the different kinds of indexing?
Indexing is a technique for determining how quickly specific data can be found.
Types:
Ø Binary search style indexing
Ø B-Tree indexing
Ø Inverted list indexing
Ø Memory resident table
Ø Table indexing

54. What is system catalog or catalog relation? How is better known as?
A RDBMS maintains a description of all the data that it contains, information about every relation and index that it contains. This information is stored in a collection of relations maintained by the system called metadata. It is also called data dictionary.

55. What is meant by query optimization?
The phase that identifies an efficient execution plan for evaluating a query that has the least estimated cost is referred to as query optimization.

56. What is join dependency and inclusion dependency?
Join Dependency:
A Join dependency is generalization of Multivalued dependency.A JD {R1, R2, ..., Rn} is said to hold over a relation R if R1, R2, R3, ..., Rn is a lossless-join decomposition of R . There is no set of sound and complete inference rules for JD.
Inclusion Dependency:
An Inclusion Dependency is a statement of the form that some columns of a relation are contained in other columns. A foreign key constraint is an example of inclusion dependency.

57. What is durability in DBMS?
Once the DBMS informs the user that a transaction has successfully completed, its effects should persist even if the system crashes before all its changes are reflected on disk. This property is called durability.

58. What do you mean by atomicity and aggregation?
Atomicity:
Either all actions are carried out or none are. Users should not have to worry about the effect of incomplete transactions. DBMS ensures this by undoing the actions of incomplete transactions.
Aggregation:
A concept which is used to model a relationship between a collection of entities and relationships. It is used when we need to express a relationship among relationships.

59. What is a Phantom Deadlock?
In distributed deadlock detection, the delay in propagating local information might cause the deadlock detection algorithms to identify deadlocks that do not really exist. Such situations are called phantom deadlocks and they lead to unnecessary aborts.

60. What is a checkpoint and When does it occur?
A Checkpoint is like a snapshot of the DBMS state. By taking checkpoints, the DBMS can reduce the amount of work to be done during restart in the event of subsequent crashes.

61. What are the different phases of transaction?
Different phases are
Ø Analysis phase
Ø Redo Phase
Ø Undo phase

62. What do you mean by flat file database?
It is a database in which there are no programs or user access languages. It has no cross-file capabilities but is user-friendly and provides user-interface management.

63. What is "transparent DBMS"?
It is one, which keeps its Physical Structure hidden from user.

64. Brief theory of Network, Hierarchical schemas and their properties
Network schema uses a graph data structure to organize records example for such a database management system is CTCG while a hierarchical schema uses a tree data structure example for such a system is IMS.

65. What is a query?
A query with respect to DBMS relates to user commands that are used to interact with a data base. The query language can be classified into data definition language and data manipulation language.

66. What do you mean by Correlated subquery?
Subqueries, or nested queries, are used to bring back a set of rows to be used by the parent query. Depending on how the subquery is written, it can be executed once for the parent query or it can be executed once for each row returned by the parent query. If the subquery is executed for each row of the parent, this is called a correlated subquery.
A correlated subquery can be easily identified if it contains any references to the parent subquery columns in its WHERE clause. Columns from the subquery cannot be referenced anywhere else in the parent query. The following example demonstrates a non-correlated subquery.
E.g. Select * From CUST Where '10/03/1990' IN (Select ODATE From ORDER Where CUST.CNUM = ORDER.CNUM)

67. What are the primitive operations common to all record management systems?
Addition, deletion and modification.
68. Name the buffer in which all the commands that are typed in are stored
‘Edit’ Buffer

69. What are the unary operations in Relational Algebra?
PROJECTION and SELECTION.

70. Are the resulting relations of PRODUCT and JOIN operation the same?
No.
PRODUCT: Concatenation of every row in one relation with every row in another.
JOIN: Concatenation of rows from one relation and related rows from another.

71. What is RDBMS KERNEL?
Two important pieces of RDBMS architecture are the kernel, which is the software, and the data dictionary, which consists of the system-level data structures used by the kernel to manage the database
You might think of an RDBMS as an operating system (or set of subsystems), designed specifically for controlling data access; its primary functions are storing, retrieving, and securing data. An RDBMS maintains its own list of authorized users and their associated privileges; manages memory caches and paging; controls locking for concurrent resource usage; dispatches and schedules user requests; and manages space usage within its table-space structures
.
72. Name the sub-systems of a RDBMS
I/O, Security, Language Processing, Process Control, Storage Management, Logging and Recovery, Distribution Control, Transaction Control, Memory Management, Lock Management

73. Which part of the RDBMS takes care of the data dictionary? How
Data dictionary is a set of tables and database objects that is stored in a special area of the database and maintained exclusively by the kernel.

74. What is the job of the information stored in data-dictionary?
The information in the data dictionary validates the existence of the objects, provides access to them, and maps the actual physical storage location.

75. Not only RDBMS takes care of locating data it also
determines an optimal access path to store or retrieve the data
76. How do you communicate with an RDBMS?
You communicate with an RDBMS using Structured Query Language (SQL)

77. Define SQL and state the differences between SQL and other conventional programming Languages
SQL is a nonprocedural language that is designed specifically for data access operations on normalized relational database structures. The primary difference between SQL and other conventional programming languages is that SQL statements specify what data operations should be performed rather than how to perform them.

78. Name the three major set of files on disk that compose a database in Oracle
There are three major sets of files on disk that compose a database. All the files are binary. These are
Ø Database files
Ø Control files
Ø Redo logs
The most important of these are the database files where the actual data resides. The control files and the redo logs support the functioning of the architecture itself.
All three sets of files must be present, open, and available to Oracle for any data on the database to be useable. Without these files, you cannot access the database, and the database administrator might have to recover some or all of the database using a backup, if there is one.

79. What is an Oracle Instance?
The Oracle system processes, also known as Oracle background processes, provide functions for the user processes—functions that would otherwise be done by the user processes themselves
Oracle database-wide system memory is known as the SGA, the system global area or shared global area. The data and control structures in the SGA are shareable, and all the Oracle background processes and user processes can use them.
The combination of the SGA and the Oracle background processes is known as an Oracle instance

80. What are the four Oracle system processes that must always be up and running for the database to be useable
The four Oracle system processes that must always be up and running for the database to be useable include DBWR (Database Writer), LGWR (Log Writer), SMON (System Monitor), and PMON (Process Monitor).
81. What are database files, control files and log files. How many of these files should a database have at least? Why?
Database Files
The database files hold the actual data and are typically the largest in size. Depending on their sizes, the tables (and other objects) for all the user accounts can go in one database file—but that's not an ideal situation because it does not make the database structure very flexible for controlling access to storage for different users, putting the database on different disk drives, or backing up and restoring just part of the database.
You must have at least one database file but usually, more than one files are used. In terms of accessing and using the data in the tables and other objects, the number (or location) of the files is immaterial.
The database files are fixed in size and never grow bigger than the size at which they were created
Control Files
The control files and redo logs support the rest of the architecture. Any database must have at least one control file, although you typically have more than one to guard against loss. The control file records the name of the database, the date and time it was created, the location of the database and redo logs, and the synchronization information to ensure that all three sets of files are always in step. Every time you add a new database or redo log file to the database, the information is recorded in the control files.
Redo Logs
Any database must have at least two redo logs. These are the journals for the database; the redo logs record all changes to the user objects or system objects. If any type of failure occurs, the changes recorded in the redo logs can be used to bring the database to a consistent state without losing any committed transactions. In the case of non-data loss failure, Oracle can apply the information in the redo logs automatically without intervention from the DBA.
The redo log files are fixed in size and never grow dynamically from the size at which they were created.

82. What is ROWID?
The ROWID is a unique database-wide physical address for every row on every table. Once assigned (when the row is first inserted into the database), it never changes until the row is deleted or the table is dropped.
The ROWID consists of the following three components, the combination of which uniquely identifies the physical storage location of the row.
Ø Oracle database file number, which contains the block with the rows
Ø Oracle block address, which contains the row
Ø The row within the block (because each block can hold many rows)
The ROWID is used internally in indexes as a quick means of retrieving rows with a particular key value. Application developers also use it in SQL statements as a quick way to access a row once they know the ROWID

83. What is Oracle Block? Can two Oracle Blocks have the same address?
Oracle "formats" the database files into a number of Oracle blocks when they are first created—making it easier for the RDBMS software to manage the files and easier to read data into the memory areas.
The block size should be a multiple of the operating system block size. Regardless of the block size, the entire block is not available for holding data; Oracle takes up some space to manage the contents of the block. This block header has a minimum size, but it can grow.
These Oracle blocks are the smallest unit of storage. Increasing the Oracle block size can improve performance, but it should be done only when the database is first created.
Each Oracle block is numbered sequentially for each database file starting at 1. Two blocks can have the same block address if they are in different database files.

84. What is database Trigger?
A database trigger is a PL/SQL block that can defined to automatically execute for insert, update, and delete statements against a table. The trigger can e defined to execute once for the entire statement or once for every row that is inserted, updated, or deleted. For any one table, there are twelve events for which you can define database triggers. A database trigger can call database procedures that are also written in PL/SQL.

85. Name two utilities that Oracle provides, which are use for backup and recovery.
Along with the RDBMS software, Oracle provides two utilities that you can use to back up and restore the database. These utilities are Export and Import.
The Export utility dumps the definitions and data for the specified part of the database to an operating system binary file. The Import utility reads the file produced by an export, recreates the definitions of objects, and inserts the data
If Export and Import are used as a means of backing up and recovering the database, all the changes made to the database cannot be recovered since the export was performed. The best you can do is recover the database to the time when the export was last performed.

86. What are stored-procedures? And what are the advantages of using them.
Stored procedures are database objects that perform a user defined operation. A stored procedure can have a set of compound SQL statements. A stored procedure executes the SQL commands and returns the result to the client. Stored procedures are used to reduce network traffic.

87. How are exceptions handled in PL/SQL? Give some of the internal exceptions' name
PL/SQL exception handling is a mechanism for dealing with run-time errors encountered during procedure execution. Use of this mechanism enables execution to continue if the error is not severe enough to cause procedure termination.
The exception handler must be defined within a subprogram specification. Errors cause the program to raise an exception with a transfer of control to the exception-handler block. After the exception handler executes, control returns to the block in which the handler was defined. If there are no more executable statements in the block, control returns to the caller.
User-Defined Exceptions
PL/SQL enables the user to define exception handlers in the declarations area of subprogram specifications. User accomplishes this by naming an exception as in the following example:
ot_failure EXCEPTION;
In this case, the exception name is ot_failure. Code associated with this handler is written in the EXCEPTION specification area as follows:
EXCEPTION
when OT_FAILURE then
out_status_code := g_out_status_code;
out_msg := g_out_msg;
The following is an example of a subprogram exception:
EXCEPTION
when NO_DATA_FOUND then
g_out_status_code := 'FAIL';
RAISE ot_failure;
Within this exception is the RAISE statement that transfers control back to the ot_failure exception handler. This technique of raising the exception is used to invoke all user-defined exceptions.
System-Defined Exceptions
Exceptions internal to PL/SQL are raised automatically upon error. NO_DATA_FOUND is a system-defined exception. Table below gives a complete list of internal exceptions.

PL/SQL internal exceptions.
PL/SQL internal exceptions.

Exception Name Oracle Error
CURSOR_ALREADY_OPEN ORA-06511
DUP_VAL_ON_INDEX ORA-00001
INVALID_CURSOR ORA-01001
INVALID_NUMBER ORA-01722
LOGIN_DENIED ORA-01017
NO_DATA_FOUND ORA-01403
NOT_LOGGED_ON ORA-01012
PROGRAM_ERROR ORA-06501
STORAGE_ERROR ORA-06500
TIMEOUT_ON_RESOURCE ORA-00051
TOO_MANY_ROWS ORA-01422
TRANSACTION_BACKED_OUT ORA-00061
VALUE_ERROR ORA-06502
ZERO_DIVIDE ORA-01476

In addition to this list of exceptions, there is a catch-all exception named OTHERS that traps all errors for which specific error handling has not been established.

88. Does PL/SQL support "overloading"? Explain
The concept of overloading in PL/SQL relates to the idea that you can define procedures and functions with the same name. PL/SQL does not look only at the referenced name, however, to resolve a procedure or function call. The count and data types of formal parameters are also considered.
PL/SQL also attempts to resolve any procedure or function calls in locally defined packages before looking at globally defined packages or internal functions. To further ensure calling the proper procedure, you can use the dot notation. Prefacing a procedure or function name with the package name fully qualifies any procedure or function reference.

89. Tables derived from the ERD
a) Are totally unnormalised
b) Are always in 1NF
c) Can be further denormalised
d) May have multi-valued attributes

(b) Are always in 1NF

90. Spurious tuples may occur due to
i. Bad normalization
ii. Theta joins
iii. Updating tables from join
a) i & ii b) ii & iii
c) i & iii d) ii & iii

(a) i & iii because theta joins are joins made on keys that are not primary keys.

91. A B C is a set of attributes. The functional dependency is as follows
AB -> B
AC -> C
C -> B
a) is in 1NF
b) is in 2NF
c) is in 3NF
d) is in BCNF

(a) is in 1NF since (AC)+ = { A, B, C} hence AC is the primary key. Since C B is a FD given, where neither C is a Key nor B is a prime attribute, this it is not in 3NF. Further B is not functionally dependent on key AC thus it is not in 2NF. Thus the given FDs is in 1NF.

92. In mapping of ERD to DFD
a) entities in ERD should correspond to an existing entity/store in DFD
b) entity in DFD is converted to attributes of an entity in ERD
c) relations in ERD has 1 to 1 correspondence to processes in DFD
d) relationships in ERD has 1 to 1 correspondence to flows in DFD

(a) entities in ERD should correspond to an existing entity/store in DFD

93. A dominant entity is the entity
a) on the N side in a 1 : N relationship
b) on the 1 side in a 1 : N relationship
c) on either side in a 1 : 1 relationship
d) nothing to do with 1 : 1 or 1 : N relationship

(b) on the 1 side in a 1 : N relationship

94. Select 'NORTH', CUSTOMER From CUST_DTLS Where REGION = 'N' Order By
CUSTOMER Union Select 'EAST', CUSTOMER From CUST_DTLS Where REGION = 'E' Order By CUSTOMER
The above is
a) Not an error
b) Error - the string in single quotes 'NORTH' and 'SOUTH'
c) Error - the string should be in double quotes
d) Error - ORDER BY clause
(d) Error - the ORDER BY clause. Since ORDER BY clause cannot be used in UNIONS

95. What is Storage Manager?
It is a program module that provides the interface between the low-level data stored in database, application programs and queries submitted to the system.

96. What is Buffer Manager?
It is a program module, which is responsible for fetching data from disk storage into main memory and deciding what data to be cache in memory.

97. What is Transaction Manager?
It is a program module, which ensures that database, remains in a consistent state despite system failures and concurrent transaction execution proceeds without conflicting.

98. What is File Manager?
It is a program module, which manages the allocation of space on disk storage and data structure used to represent information stored on a disk.

99. What is Authorization and Integrity manager?
It is the program module, which tests for the satisfaction of integrity constraint and checks the authority of user to access data.

100. What are stand-alone procedures?
Procedures that are not part of a package are known as stand-alone because they independently defined. A good example of a stand-alone procedure is one written in a SQL*Forms application. These types of procedures are not available for reference from other Oracle tools. Another limitation of stand-alone procedures is that they are compiled at run time, which slows execution.
 

101. What are cursors give different types of cursors.
PL/SQL uses cursors for all database information accesses statements. The language supports the use two types of cursors
Ø Implicit
Ø Explicit

102. What is cold backup and hot backup (in case of Oracle)?
Ø Cold Backup:
It is copying the three sets of files (database files, redo logs, and control file) when the instance is shut down. This is a straight file copy, usually from the disk directly to tape. You must shut down the instance to guarantee a consistent copy.
If a cold backup is performed, the only option available in the event of data file loss is restoring all the files from the latest backup. All work performed on the database since the last backup is lost.
Ø Hot Backup:
Some sites (such as worldwide airline reservations systems) cannot shut down the database while making a backup copy of the files. The cold backup is not an available option.
So different means of backing up database must be used — the hot backup. Issue a SQL command to indicate to Oracle, on a tablespace-by-tablespace basis, that the files of the tablespace are to backed up. The users can continue to make full use of the files, including making changes to the data. Once the user has indicated that he/she wants to back up the tablespace files, he/she can use the operating system to copy those files to the desired backup destination.
The database must be running in ARCHIVELOG mode for the hot backup option.
If a data loss failure does occur, the lost database files can be restored using the hot backup and the online and offline redo logs created since the backup was done. The database is restored to the most consistent state without any loss of committed transactions.

103. What are Armstrong rules? How do we say that they are complete and/or sound
The well-known inference rules for FDs
Ø Reflexive rule :
If Y is subset or equal to X then X Y.
Ø Augmentation rule:
If X Y then XZ YZ.
Ø Transitive rule:
If {X Y, Y Z} then X Z.
Ø Decomposition rule :

If X YZ then X Y.
Ø Union or Additive rule:
If {X Y, X Z} then X YZ.
Ø Pseudo Transitive rule :
If {X Y, WY Z} then WX Z.
Of these the first three are known as Amstrong Rules. They are sound because it is enough if a set of FDs satisfy these three. They are called complete because using these three rules we can generate the rest all inference rules.

104. How can you find the minimal key of relational schema?
Minimal key is one which can identify each tuple of the given relation schema uniquely. For finding the minimal key it is required to find the closure that is the set of all attributes that are dependent on any given set of attributes under the given set of functional dependency.
Algo. I Determining X+, closure for X, given set of FDs F
1. Set X+ = X
2. Set Old X+ = X+
3. For each FD Y Z in F and if Y belongs to X+ then add Z to X+
4. Repeat steps 2 and 3 until Old X+ = X+

Algo.II Determining minimal K for relation schema R, given set of FDs F
1. Set K to R that is make K a set of all attributes in R
2. For each attribute A in K
a. Compute (K – A)+ with respect to F
b. If (K – A)+ = R then set K = (K – A)+

105. What do you understand by dependency preservation?
Given a relation R and a set of FDs F, dependency preservation states that the closure of the union of the projection of F on each decomposed relation Ri is equal to the closure of F. i.e.,
((PR1(F)) U … U (PRn(F)))+ = F+
if decomposition is not dependency preserving, then some dependency is lost in the decomposition

106. What is meant by Proactive, Retroactive and Simultaneous Update.
Proactive Update:
The updates that are applied to database before it becomes effective in real world .
Retroactive Update:
The updates that are applied to database after it becomes effective in real world .
Simulatneous Update:
The updates that are applied to database at the same time when it becomes effective in real world .

107. What are the different types of JOIN operations?
Equi Join: This is the most common type of join which involves only equality comparisions. The disadvantage in this type of join is that there

Database Concepts or Database Keywords

Data Mart - A single star schema, i.e. dimensions and a fact table that stores data at the detail level. A Data Mart covers a specific area of the business: billing, inventory, transactions, claims, etc.

Data Modeling - Performing analysis on the business processes and data to discover attributes of, and relationships between, data elements. An Entity Relationship Diagram (ERD) is the implementation of a data model. Another way to think of it is to discover the business rules of the data elements.

Data Warehouse - The data warehouse to me is more of a logical concept. All of your data marts (with, hopefully conformed dimensions) plus any ODS or active staging areas. By active, I mean updated in real-time by operational systems primarily in support of the warehouse. To me the warehouse is all of the systems that are required to answer the end users' decision support questions across an enterprise. This is different than the Enterprise Data Warehouse (EDW) that is the granddaddy data source for all decision support. A data warehouse can reside in a single data or in many databases.

Dimension - A textual table in a star schema. The textual data describes a fact. Dimensions are the context of a measurement (fact). The dimensions included in the primary key of a fact table implement the grain of the fact table.

Dimensional Modeling - Data Modeling with the goal of extracting facts and defining descriptions of those facts from business systems. The relationships between data elements should be known before Dimensional Modeling starts (by previously performing Data Modeling to, at least, the entity level).

DML - Data Manipulation Language. Language used to add (insert), update, or delete records in a database table.

Fact - Measurement. In general, it is the numeric value that is acted upon by a user using a data mart.

Foreign Key - A foreign key (FK) is a link between two tables, i.e. a child or parent record. A foreign key is usually link to a primary key in a different table.

Index - A narrow table, usually containing a subset of a table's columns, to speed access to a particular record or set of records. An example would be an index on a name field if you frequently search on the name column.

Natural Key - A natural key is a key that has meaning. An employee's social security number might be used to uniquely identify employees in an HR system (I would NOT recommend this but I have seen it). That would be a natural key.

ODS - Operational Data Store. An ODS exists primarily when data quality is less than optimal. When an operational system cannot provide clean data, it can feed an ODS where the data is cleansed and/or transformed. An ODS is optional and is not a focal point of the warehouse. An ODS can have many sources of data and there can be many ODSs.

OLAP - Online Analytical Processing. Now called Business Intelligence (BI) for the most part. This includes data mining. OLAP used to be the queries that took hours to run but more and more OLAP is happening in real-time. OLAP is extracting historical, statistical, etc. information from the raw data.

OLTP - Online Transaction Processing. This used to be synonymous with real-time processing but now everything needs to happen in real-time. OLTP tends to be single, small statements from end point applications, i.e. POS, Entry Screens, embedded devices, log files, etc.

Oracle Designer - CASE tool developed by oracle. Designer is an end-to-end database design tool. I personally use it for its ERD functionality. At times I feel like even that is way too cumbersome.

Primary Key - A primary Key (PK) uniquely identifies a single row in a table.

Relational Database - RDBMS. A data store designed to store data in tables and columns with pre-defined relationships between tables. Primary and foreign keys define relationships.

Replication - Copying data from one database to another (Publisher and Subscriber Concept).

Schema - A set of related database objects. An HR schema would store personnel and payroll information; a GL schema would store the chart of accounts, etc.

Surrogate Key - A surrogate key is a sequential number that is meaningless. In oracle it's usually created by a sequence.

.NET INTEGRATION WITH SQL SERVER 2005

 

 

• What are steps to load a .NET code in SQL SERVER 2005?
Write the managed code and compile it to a DLL/Assembly.
After the DLL is compiled using the "CREATE ASSEMBLY" command you can load the assemby into SQL SERVER. Below is the create command which is loading "mycode.dll" into SQL SERVER using the "CREATE ASSEMBLY" command
Syntax
CREATE ASSEMBLY AssemblyName FROM 'C:/MyAssmbly.dll'

• How can we drop an essembly from SQL SERVER?
DROP ASSEMBLY AssemblyName

• Are changes made to assembly updated automatically in database?
No, it will not synchronize the code automatically. For that you have to drop the assembly (Using DROP ASSEMBLY) and create (Using the CREATE ASSEMBLY again)

• Why do we need to drop assembly for updateing changes?
When we load the assembly into SQL SERVER, it stores into the sys.assemblies system table. So any changes after that to the external DLL/ASSEMBLY will not reflect in SQL SERVER. So we have to DROP and CREATE assembly again in SQL SERVER.

• How to see assemblies loaded in SQL SERVER?
SELECT * FROM sys.assemblies_files

• If I want to see which files are linked with which assemblies?
Use sys.Assemblies_files system tables have the track about which files are associated with what assemblies.
SELECT * FROM sys.assemblies_files

• Does .NET CLR and SQL SERVER run in different process?
.NET CLR engine (hence all the .NET applications) and SQL SERVER run in the same process or address space. This "Same address space architecture" is implemeted so that there no speed issues. If the architecture was implemented the other way (i.e. SQL SERVER and .NET CLR engine running in different memory process area) there would have been reasonable speed issue.

• Does .NET controls SQL SERVER or is it vice-versa?
SQL SERVER controls the way .NET application will run. Normally .NET framework controls the way application should run. But in order that we have high stability and good security SQL SERVER will control the way .NET frame work works with SQL SERVER environment. So lot of things will be controlled through SQL SERVER example: threads, memory allocations, security etc.

SQL SERVER can control .NET framework by "Host Control" mechanism provided by .NET Framework 2.0. Using the "Host Control" framework external application's can control the way memory management is done, thread allocation's are done and lot more. SQL SERVER uses "host Control" mechanism exposed by .NET 2.0 and controls the framework.

• Is SQLCLR configured by default?
SQLCLR is not configured by default. If Developers want to use the CLR integration feature of SQL SERVER it has to be enabled by DBA (From the Surface Area Configuration).

• How to configigure CLR for SQL SERVER?
It's a advanced option you will need to run the following query Analyzer

EXEC Sp_configure 'show advaced option', '1''; go reconfigure go
EXEC Sp_configure 'clr enabled', '1' go reconfigure; go
EXEC Sp_configure 'show advanced options', '1'; reconfigure
EXEC sp_configure' clr enabled' ' '1' reconfigure

• Is .NET feature loaded by default in SQL SERVER?
NO it will not be loaded, CLR is lazy loaded that means its only loaded when needed. It goes one step ahead. where the database Administrator has to turn the feature and using the "SP_Configure".

NOTE: Loading .NET programming consumes some memory resources around 20 to 30 MB(it may vary depending on lot of situations). So if you really need .NET Integration then only go for this option.

• How does SQL Server control .NET at run-time?
.NET CLR exposes interfaces by which an external host can control the way .NET rum time runs. In previous versions of .NET it was done via COM interface "ICorRuntimeHost".
In previous version you can only do the following with COM interface.

* Specify that whether its server or work station DLL
* Specify version of the CLR (e.g.version 1.1 or 2.0)
* Specify garbage collection behavior
* Specify whether or not jitted cod emay be shared across AppDomains.

In .NET 2.0 it's done by "ICLRRuntimeHOST" But in .NET 2.0 you can do much above that was provided by the previous COM interface

* Exceptional conditions
* Code loading
* Class loading
* Security particulars
* Resource allocation

SQL Server uses the "ICLRRuntimeHOST" to control .NET run time as the flexibility provided by the interface is far beyond what is given by the previous .NET version, and that 's what exactly SQL Server needs, a full control of the .NET run time.

• What's a "SAND BOX" in SQL SERVER 2005?
"Sand box is a safe place for running semi-trusted programs or scripts, often originationg from the a third party"

Now for SQL SERVER it's .NET the external third party which is running and SQL SERVER has to be sure that .NET runtime crashes does not affect his working. So in order that SQL Server runs properly there are three sandboxes that user code can run:

Safe Access sandbox: This will be the favorite setting of DBA's if they are compelled to run CLR- Safe access Safe means you have only access to in-proc data access functionalities. So you can create stored procedures, triggers, functions, data types, triggers etc. But you can not access memory, disk, create files etc. In short you ca not hang the SQL Server.

External access sandbox: In External access you can use some real cool features of .NET like accessing file systems outside box, you can leverage your classes etc. But here you are not allowed to play around with threading, memory allocation etc.

Unsafe access sandbox:In Unsafe access you have access to memory management, threading,etc. So here developers can write unreliable and unsafe code which destabilizes SQL Server. In the first two access levels of sand box its difficult to write unreliable and unsafe code.