28.4.08

Thanking Mail from dotnetspider moderator

OOPs, Today morning i got a thanking mail from dotnet spider moderator for helping them. Below is the mail,

From: asha mathews [mailto:ashamathew19@yahoo.co.u]
Sent: Tue 4/29/2008 8:03 AM
To: Venkatesan Prabu J
Cc: webmaster
Subject: message from .net spider

Hello Venkatesh,
Good morning, Thanks for supporting dotnetspider in tracing copied contents and encouraging genuine articles. The copied article which you have reported is deleted. We are looking forward to get the same help and support from you.
Thanks
Asha mathews
Web Master @ dotnetspider

27.4.08

Dynamically naming the table

I've got a peculiar problem to create tables with dynamic table name.

Problem statement:

Consider an employee database in which i have to create table for each employee on each date. The table name should be given dynamically at run time. I want to create based table name based on the input.

Solution statement:

Create a stored procedure with input parameters as table name.
Construct a dynamic query for creating the table.
Execute the dynamic query.


CREATE PROCEDURE TableNameAssigningProcedure
(@EmployeeTableName varchar(100))
AS
BEGIN
DECLARE @CMD nVARCHAR(100),@AppendString VARCHAR(8)
SELECT @AppendString = CONVERT(VARCHAR(8), GETDATE(), 12)
SELECT @CMD=N'CREATE TABLE '+ @EmployeeTableName+ @AppendString + '(ID INT,NAME VARCHAR(50))'
PRINT @CMD
exec SP_EXECuteSQL @CMD
END


EXEC TableNameAssigningProcedure 'SANTHI'


SELECT * FROM "Newly created table"

Regards,
Venkatesan Prabu . J

Cleared my MCITP exam

On 25th April, i have cleared my microsoft exam 70-444 with 98.4%

Checked with microsoft site for MCITP degree holders. I am one among the 4,433 candidates to complete this certification world wide. Good news naaa...........
For getting MCITP, we have to write the below two exams,
70-443 - PRO: Designing a Database Server Infrastructure by Using Microsoft SQL Server 2005
70- 444 - PRO: Optimizing and Maintaining a Database Administration Solution by Using Microsoft SQL Server 2005

Happy learning!!!
Regards,

Venkatesan Prabu . J

25.4.08

Download Adventureworkdw database

I have got a query regarding installation of adventureworksdw.

Please check the below link provided by Microsoft to install these sample databases,

http://msdn2.microsoft.com/en-us/library/ms143804.aspx

Download Adventure works Database,

http://www.microsoft.com/downloads/details.aspx?FamilyId=E719ECF7-9F46-4312-AF89-6AD8702E4E6E&displaylang=en

Regards,
Venkatesan Prabu . J

23.4.08

Subquery Vs Joins

Got a request from dotnet spider user regarding query performance. In the below query, which one is best?

  • select * from table1 where id in (select id from table2)
  • select a.* from table1 a,table2 b where a.id=b.id
  1. Subqueries are usually slower when compared to the ordinary SQL queries.
  2. Two seperate execution happens in the first query, first the subquery will execute to fetch the data from table2, second the comparison with the data from the table1 happens to obtain the exact output.

Regards,

Venkatesan Prabu . J

22.4.08

Retrieving information about last backup date of all databases in the server

We can get the general information about the databases from master.sys.sysdatabases


select * from master.sys.sysdatabases

For every backup process an entry will be added into the msdb.dbo.backupset. Below is the query to retreive the backup details.


select * from msdb.dbo.backupset

To retrieve the backup information, we can query backupset table from msdb database.


select Database_name,
COALESCE(Convert(varchar(20), MAX(backup_finish_date), 101),'Backup Not Taken') as
LastBackUpTakenDate,
COALESCE(Convert(varchar(20), MAX(user_name), 101),'NA') as BackupTakenUser
from msdb.dbo.backupset
GROUP BY Database_name
Else, we can go for joining two tables(one from master database and another from msdb database). Below is the query to achieve the same,


SELECT
Tab1.Name as DbName,
COALESCE(Convert(varchar(20), MAX(Tab2.backup_finish_date), 101),'Backup Not Taken') as
LastBackUpTakenDate,
COALESCE(Convert(varchar(20), MAX(Tab2.user_name), 101),'NA') as BackupTakenUser
FROM sys.sysdatabases Tab1 LEFT OUTER JOIN msdb.dbo.backupset Tab2
ON Tab2.database_name = Tab1.name
GROUP BY Tab1.Name
ORDER BY Tab1.Name

Sample Output:











Happy learning!!!
Regards,
Venkatesan Prabu. J

10.4.08

Atlast Cleared my MCP 070-443 exam

I am very happy to share this info, i've cleared one of the MCITP paper

070-443 - Designing a database server infrastructure by using microsoft sql server 2005.

It's little bit tough to clear this exam. However, i have managed to hit 940 out of 1000.

Regards,
Venkatesan Prabu . J

9.4.08

Boosting replies on my blog


Sure, I will make it out from my next posts.
Regards,
Venkatesan Prabu . J

T-SQL Challenges - Part 3 - Temporary tables

Digging into the logics behind Temporary tables in sql server:
I have noticed many interesting articles on temporary table in sql server.
But, this article provides some unknown facts on sql server.
Assuring you an interesting fact on sql server temporary table.
Know about Temporary table:
Temporary tables are special tables created in temp database. It has a prefix '#' for local temporary table
or "##" for global temporary table.
The temporary table will get deleted if the session is expired or the server restarts.
Local temporary table: This can be used with in a specific object and cannot be
shared with other system objects. Each table is associated with a specific session id
and we cannot use it in another session.
For ex: I am creating a temporary table A in the stored procedure SP1, If i try to
use the same temporary table in another stored procedure SP2. It won't work because
its not in this specific scope. To recover this problem, we have to Global temporary table.
Global temporary table: Its nothing but a global table accessed by different
system objects.
Ok, am stopping all those basics and lets enter into some R&D work,
I had a situation to construct a temporary table using dynamic SQL. OOPS!! am finding some
strange problem to achieve it. Let's see the code,
Code Snippet
declare @string varchar(1000)
set @string = 'SELECT * INTO #TempTable FROM dbo.SAMPLE'
exec (@string)
SELECT * from #TempTable

I am getting the following error,
"Invalid object name '#TempTable'."
I wondered to see this message and started checking the syntax, but everything is
ok and i don't find any way to fix this problem.
I've tried with ordinary table,
Code Snippet
declare @string varchar(1000)
set @string = 'SELECT * INTO TempTable FROM dbo.SAMPLE'
exec (@string)
SELECT * from TempTable
OOPS, its working fine.
But my business functionality forces me to create a temporary table. I don't find
any other way to go,
Code Snippet
declare @string varchar(1000)
create table #TempTable(id int)
set @string = 'insert INTO #TempTable select id FROM dbo.SAMPLE'
exec (@string)
SELECT * from #TempTable
Atlast, i got some other way to achieve the same. But, i dont know what's the exact problem lies behind.
Digging towards it, i found some other way.
I resolved the problem by using global temporary table instead of local temporary table
It's working fine.
Code Snippet
declare @string varchar(1000)
set @string = 'SELECT * INTO ##TempTable FROM dbo.SAMPLE'
exec (@string)
SELECT * from ##TempTable
Solution statement:
After a thorough search, i found that the problem lies with the exec statement.
Exec statement will try to create a seperate session and my local temporary table
won't lie in this newly created session.
Interesting right!!!!!
Happy learning.
Regards,
Venkatesan Prabu . J

5.4.08

T-SQL Challenges - Part 2

Query Problem:
Got this problem from MSDN user in microsoft site. Wish to solve this problem.
Is it possible to append the result sets as a single column or result set seperated by comma.
Table Structure
Name Age
venkat 10
arun 20
prabu 30
Output:
venkat,10,arun,20,prabu,30
Sample Query to solve this problem:
Code Snippet

create table VenkatSampleTable(name varchar(100),age int)
insert into VenkatSampleTable values ('venkat',10)
insert into VenkatSampleTable values ('arun',20)
insert into VenkatSampleTable values ('prabu',30)

declare @values as varchar(500)
set @values = ''

select @values = @values + name + ','+cast(age as varchar(50)) + ','from VenkatSampleTable

select substring(@values,1,len(@values)-1)
Its the easiest and fastest way to append the result set.
Happy learning!!!
Regards,
Venkatesan Prabu . J

3.4.08

T-SQL Challenges - Part 1 -Pivot Operator

Problematic statement:
Consider two table 1 and 2 and they are linked by a common column "ID".
Table1 had the details about the person and table2 list down the scores availed by the person.
My problem is to combine these two table listing out the person and their marks in each subjects.
Assumptions:
In table2, the rows are added as per the subjects, first mark will be considered as subject1,
second mark will be considered as subject2,Thrid mark will be considered as subject3.
Below are the sample inputs and expected outputs,
SQLTable1:
Code Snippet

ID StudentName
1 Venkatesan
2 Arun
3 Santhi
4 Vijay

SQLTable2:
Code Snippet

ID Marks
1 90
1 20
1 80
2 78
2 67
3 89
3 65
3 98
4 78
4 76
4 45

Expected output from the above tables
Code Snippet

ID StudentName Sub1 Sub2 Sub3
---------------------------------------------------------

1 Venkatesan 90 20 80
2 Arun 78 67 NULL
3 Santhi 89 65 98
4 Vijay 78 76 45


Solution:
Microsoft sql server 2005 provides a very handy option of altering the rows to columns
using pivot property. To solve the above problem,
1. First we have to create a cte listing the rownumber partitioned by ID.
2. Pivot the data based on rownumber.
Code Snippet

--Creating table variables
declare @SQLTable1 table (id int,Studentname varchar(100))
declare @SQLTable2 table (id int,Marks int)
-- inserting the data into the table variables
insert into @SQLTable1
select '1','Venkatesan' union all
select '2','Arun' union all
select '3','Santhi' union all
select '4','Vijay'

insert into @SQLTable2
select '1','90' union all
select '1','20' union all
select '1','80' union all
select '2','78' union all
select '2','67' union all
select '3','89' union all
select '3','65' union all
select '3','98' union all
select '4','78' union all
select '4','76' union all
select '4','45'

--select * from @SQLTable1
--select * from @SQLTable2
--Creating rownumber in the cte
;with VenkatCTE as(

select a.id,a.Studentname, b.Marks,
row_number() over ( partition by a.id order by a.id) as rn
from @SQLTable1 a inner join @SQLTable2 b on a.id=b.id
)
--select * from VenkatCTE
-- pivoting the rows in the cte
select id,Studentname,[1] as Subject1,[2] as Subject2,[3] as Subject3
from VenkatCTE
pivot
(
min(Marks) for rn in ([1],[2],[3])
)
pvt
order by id

Happy learning!!!
Regards,
Venkatesan Prabu . J

2.4.08

Table value parameters in SQL Server 2008

USER DEFINED TABLE TYPES IN SQL SERVER 2008:

It's a new T-SQL enhancements done in sql server 2008 which allows us to pass the table as parameters for our stored procedure. In the client server architecture we used to pass individual rows from the front end and its get updated in the backend. Instead of passing individual rows, Microsoft released a new enhancement referred to as table value parameters where they are providing a flexibility to pass the table as a parameter from the front end.

Features:

1. Processing speed will be comparitively very faster.
2. We have to declare the table as a Readonly one. DML operations cannot be done on the table.
3. From the front end we have to pass the data in the form of structures.
4. Reduces roundtrip to the server
5. Processes complex logics at a stretch in one single routine.

Code Snippet

-- Am trying to create a table "EmployeeTable" with three fields.
CREATE TABLE EmployeeTable
(id int,
[name] varchar(100),
designation varchar(100))

-- Creating a stored procedure "TableValuedSampleProc" to insert the rows.
CREATE PROCEDURE TableValuedSampleProc (@id int, @name varchar(100),@designation varchar(100))
AS
BEGIN
insert into EmployeeTable values (@id,@name,@designation)
END
-- Executing the stored procedure
EXEC TableValuedSampleProc 1,'VENKAT','LEAD ENGINEER'
EXEC TableValuedSampleProc 2,'ARUN','DEVELOPER'
EXEC TableValuedSampleProc 3,'SUBA','LEAD ENGINEER'

SELECT * FROM EmployeeTable

-- Am trying to create a table type "EmployeeTableType"
CREATE TYPE EmployeeTableType AS TABLE
(ID int, [name] varchar(100),designation varchar(100))

-- Creating the stored procedure in insert the data using Table type.
CREATE PROCEDURE EmployeeTableTypeProc (@EmployeeTempTable EmployeeTableType READONLY)
AS
BEGIN
INSERT INTO EmployeeTable
SELECT * FROM @EmployeeTempTable
END
-- Building a temporary table type
DECLARE @TempEmployee EmployeeTableType
INSERT INTO @TempEmployee VALUES (1,'VENKAT','LEAD ENGINEER')
INSERT INTO @TempEmployee VALUES (2,'ARUN','DEVELOPER')
INSERT INTO @TempEmployee VALUES (3,'SUBA','LEAD ENGINEER')

-- Executing the stored procedure by passing the temporary table type
EXEC EmployeeTableTypeProc @TempEmployee

-- Checking the existence of data
SELECT * FROM EmployeeTable


Please provide me your valuable feedback.
Regards,
Venkatesan Prabu . J

My T-SQL Gallery @code.msdn.microsoft


Created my own T-SQL Gallery in Microsoft site. Do visit the same and share your feedback,

http://code.msdn.microsoft.com/VenkatSQLSample/Thread/List.aspx

Thanks and Regards,
Venkatesan Prabu .J

SQL Server Interview questions - Part 1

What is the significance of NULL value and why should we avoid permitting null values?
Null means no entry has been made. It implies that the value is either unknown or undefined.We should avoid permitting null values because Column with NULL values can't have PRIMARY KEY constraints. Certain calculations can be inaccurate if NULL columns are involved.

What is SQL whats its uses and its component ?
The Structured Query Language (SQL) is foundation for all relational database systems. Most of the large-scale databases use the SQL to define all user and administrator interactions. It enable us to retrieve the data from based on our exact requirement. We will be given a flexibility to store the data in our own format.


The DML component of SQL comprises four basic statements:
* SELECT to get rows from tables
* UPDATE to update the rows of tables
* DELETE to remove rows from tables
* INSERT to add new rows to tables


What is DTS in SQL Server ?
Data Transformation Services is used to transfer the data from one source to our required destination. Considering am having some data in sql server and I need to transfer the data to Excel destination. Its highly possible with dialogue based tool called Data Transformation services. More customization can be achieved using SSIS. A specialized tool used to do such migration works.


What is the difference between SQL and Pl/Sql ?

Straight forward. SQL is a single statement to finish up our work.Considering, I need some data from a particular table. “Select * from table” will fetch the necessary information. Where as I need to do some row by row processing. In that case, we need to go for Procedural Logic / SQL.

What is the significance of NULL value and why should we avoid permitting null values?
Null means no entry has been made. It implies that the value is either unknown or undefined.We should avoid permitting null values because Column with NULL values can't have PRIMARY KEY constraints. Certain calculations can be inaccurate if NULL columns are involved.

Difference between primary key and Unique key?
Both constraints will share a common property called uniqueness. The data in the column should be unique. The basic difference is,
· Primary key won’t allow null value. Whereas, unique key will accept null value but only one null value.
· On creating primary key, it will automatically format the data inturn creates clustered index on the table. Whereas, this characteristics is not associated with unique key.
· Only one primary key can be created for the table. Any number of Unique key can be created for the table.

Select Statement in SQL Server

Select Statement in SQL Server

String Functions in sql server

String Functions in sql server
Substring/Len/replace/Ltrim/Rtrim

SQL Server Interview Question - Part 2

What is normalization?

Normalization is the basic concept used in designing a database. Its nothing but, an advise given to the database to have minimal repetition of data, highly structured, highly secured, easy to retrieve. In high level definition, the Process of organizing data into tables is referred to as normalization.


What is a stored procedure:
Stored procedures are precompiled T-SQL statements combined to perform a single task of several tasks. Its basically like a Macro so when you invoke the Stored procedure, you actually run a set of statements. As, its precompiled statement, execution of Stored procedure is compatatively high when compared to an ordinary T-SQL statement.


What is the difference between UNION ALL Statement and UNION ?
The main difference between UNION ALL statement and UNION is UNION All statement is much faster than UNION,the reason behind this is that because UNION ALL statement does not look for duplicate rows, but on the other hand UNION statement does look for duplicate rows, whether or not they exist.

Example for Stored Procedure?
They are three kinds of stored procedures,1.System stored procedure – Start with sp_2. User defined stored procedure – SP created by the user.3. Extended stored procedure – SP used to invoke a process in the external systems.Example for system stored proceduresp_helpdb - Database and its propertiessp_who2 – Gives details about the current user connected to your system. sp_renamedb – Enable you to rename your database


What is a trigger?

Triggers are precompiled statements similar to Stored Procedure. It will automatically invoke for a particular operation. Triggers are basically used to implement business rules.


What is a view?
If we have several tables in a db and we want to view only specific columns from specific tables we can go for views. It would also suffice the needs of security some times allowing specfic users to see only specific columns based on the permission that we can configure on the view. Views also reduce the effort that is required for writing queries to access specific columns every time.


What is an Index?
When queries are run against a db, an index on that db basically helps in the way the data is sorted to process the query for faster and data retrievals are much faster when we have an index.


What are the types of indexes available with SQL Server?

There are basically two types of indexes that we use with the SQL ServerClustered -

1. It will format the entire table, inturn physically sort the table.

2. Only one clustered index can be created for a table.

3. Data will be located in the leaf level.

4. By default, primary key will create clustered index on the table.

Non-Clustered Index

1. It wont touch the structure of the table.

2. It forms an index table as reference to the exact data.

3. A reference to the data will be located in the leaf level.

4. For a table, we can create 249 non clustered index.

Happy Learning!!!
Regards,
Venkatesan Prabu .J

SQL Interview question

Extent Vs Page?

Pages are low level unit to store the exact data in sql server. Basically, the data will be stored in the mdf, ldf, ndf files. Inturn, pages are logical units available in sql server.The size of the page is 8KB.

Eight consecutive pages will form an extent 8 * 8KB = 64KB.

Thus I/O level operation will be happening at pages level.The pages will hold a template information at the start of each page (header of the page).

They are,

1. page number,

2. page type,

3. the amount of free space on the page,

4. the allocation unit ID of the object that owns the page.

Extents will be classifed into two types,

1. Uniform extents

2. Mixed extents

Uniform Extents:It occupied or used by a single object. Inturn, a single object will hold the entire 8 pages.Mixed

Extents:Mulitple objects will use the same extent. SQL Server will allow a max of eight objects to use a shared extent.

Property of SQL Server :Initally if an object is created, sql server will allocate the object to the mixed extent and once if the size reaches 8 pages and more... immediately, a new uniform extent will be provided for that particular object.

Herecomes, our fragmentation and reindexing concepts.

Best Joke - Enjoy it

Best Joke - Enjoy it