28.2.09

To get last record in the table

Thanks and Regards,
Venkatesan Prabu .J

Checking appropriate row in the secondary table in reference to the primary table

I got a peculiar query to fetch the rows from the table + check for the same value in the secondary table.
1. The condition is only one select query to fetch it.
2. Input parameters will be passed.
This can be achieved by co-related query concept. Am thinking for any other alternative on this. May be, I will place it in my future articles.

create table mysampletable (id int,name1 varchar(100))
insert into mysampletable values(1,'Venkat')
insert into mysampletable values(2,'Venkat1')
insert into mysampletable values(3,'Venkat2')
insert into mysampletable values(4,'Venkat3')

create table mysampletable1 (id int,name1 varchar(100))
insert into mysampletable1 values(1,'Venkat')
insert into mysampletable1 values(2,'Venkat1')
insert into mysampletable1 values(3,'Venkat2')
insert into mysampletable1 values(4,'Venkat3')

select * from mysampletable
select * from mysampletable1

select *,(select count(*) from mysampletable1 where mysampletable1.id=mysampletable.id) as 'Rowexistsin Secondtable'
from mysampletable where mysampletable.id =1
Thanks and Regards,
Venkatesan Prabu .J

23.2.09

Joining three tables in SQL Server

Below is the sample to join three tables in sql server.

Happy Learning!!!

Regards,
Venkatesan Prabu .J

File System task - Renaming the file

Let see some interesting facts in SSIS,

File system tasks is a nice task used to do our operations on the files in operating system level. Using file system task, we can transfer the file from one place to another (By specifying the source and destination), directory level manipulations and assigning the property to a file.

Lets see a small demo on file system task, I am trying to rename the file located in my desktop.

My existing file name is venkat.txt and i am trying to rename it to venkat1.txt. Drag file sytem tasks and double click it. In the properties window, provide necessary source and destination path of the file. Specify the operation to be done on the file.

Once the file connections were specified(source and destination), you will get the file connection in your packages.


right click on the task and execute it. Now, you file got renamed.
Happy Learning!!!
Thanks and Regards,
Venkatesan Prabu .J

19.2.09

Get the current designation of an employee in sql server

Scenario: I want to fetch the latest role of employee and the employee id

drop table emp
drop table emprole
create table Emp(Employeeid int, roleid int,Updtdate datetime)
create table EmpRole(Roleid int, RoleName varchar(10))


insert into emp values(1,33,'2008-10-11')
insert into emp values(1,44,'2008-10-13' )
insert into emp values(2,55,'2008-10-14')
insert into emp values(2,66,'2008-10-16')

insert into emprole values(33, 'Mgr')
insert into emprole values(44, 'Dev')
insert into emprole values(55, 'Tester')
insert into emprole values(66, 'Lead')

select * from Emp
select * from EmpRole
select * from
(
select Employeeid, row_number() over (partition by employeeid
order by UpdtDate desc) as row ,r.rolename
from emp e inner join emprole r on e.roleid=r.roleid
)tblw where row=1

drop table Emp
drop table EmpRole




Thanks and Regards,

Venkatesan Prabu .J

18.2.09

Row_number in SQL Server 2005

An article on Rownumber:



Usually we used to find some peculiar scenarios like below,


An employee is frequently shifting to different places. I need to fetch all the employees recent location. Considering an employee is working in texas, a record will be added. Now, the employee got shifted to newyork. I need to list the employees recent location. How can i achieve it

create table venkat1
(id int, name1 varchar(100),name2 varchar(100))
insert into venkat1 values(1,'Venkat','Venkat1')
insert into venkat1 values(2,'Venkat1','Venkat2')
insert into venkat1 values(3,'Venkat1','Venkat3')
insert into venkat1 values(4,'Venkat','Venkat4')
select * from venkat1

select id,name1 from
(select id, row_number() over (partition by name1 order by id desc) as row, name1
from venkat1 )tbl where row=1





Thanks and Regards,
Venkatesan Prabu .J

3.2.09

Like operator in SQL Server

Pattern matching in SQL Server:

Pattern matching is a very good area and its very well needed for searching our related data in our database. Considering, I need to check the person name starts with A. In this case, we can opt like operator in SQL Server to retrieve those related patterns.

Below is an example,


drop table venkat
create table venkat(id int, name varchar(10))
insert into venkat
select 1,'Venkat'
union all
select 2,'arun'
union all
select 3,'Lakshmi'
union all
select 4,'arun'
union all
select 5,'ve'

Let's see some of the pattern mathching conditions


String Starts with "V" and having any number of characters. % indicates any number of character
select * from venkat where name like 'V%' - No ouput
String Starts with "V" and having only one character. _ indicates only one number.
select * from venkat where name like 'V_' - 5 for id and ve for name
String should not start with "V"
select * from venkat where name not like 'V%'

Happy Learning!!!
Regards,
Venkatesan Prabu .J

SQL Server Error

Error Message:
Msg 8152, Level 16, State 14, Line 4
String or binary data would be truncated.

Example:
create table venkat(id int, name varchar(10))
insert into venkat
select 1,'Venkat'
union all
select 2,'arun'
union all
select 3,'Lakshmifdsaf'
union all
select 2,'arun'

You are trying to insert the data, which is beyond the allowable size. The data "Lakshmifdsaf" will hold more size when compared to the allowable size.

Happy Learning!!!
Regards,
Venkatesan Prabu .J

CASE Operator in SQL Server

CASE Operator:

Scenario:

We used face a regular scenario to update the values based on the data available in the table. For this kind of situation, we can go for CASE operator.

Sytax:

Case


when expresssion or column1 = value1 Then assign this value to column1


when expresssion or column1 = value2 Then assign this value to column1


end


Example:

Am trying to create a table,
drop table venkat
create table venkat(id int, nam varchar(10))
insert into venkat values (1,'a')
insert into venkat values (2,'aa')
insert into venkat values (3,'aaa')
select * from venkat

select * from
(
select idval =
case id
when 1 then '1a'
when 2 then '2a'
when 3 then '3a'
end
from venkat
)tbl

The output resembles,

Thanks and Regards,

Venkatesan Prabu .J

SQL Puzzle - Small things to remember

Today, I have tried some interesting tiny concepts like,

I am assigning a value to a variable and it should be bound to a specific column.
Whether I need.
1. Assign the value and bind it to a column or Whether this one will work
2. Bind to a column and afterwards assign it to a column. Whether this one will work

Lets make a try,
Now, am declaring a variable and binding it to a column and afterwards am trying to set the variable. OOPs, the value is not reflecting.

declare @a varchar(10)
select @a "ColumnName"
set @a='venkat'
print @a

Let's try for an alternative, assign the value and bound it to the column.


declare @a varchar(10)
set @a='venkat'
select @a "ColumnName"
print @a

Yes, its working. As a basic foundation thoughts, the variables should be assigned with a value and afterwards we need to bound it to a columnname.

Happy Learning!!!

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