Execute Dynamic SQL commands in SQL Server

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In some applications having hard-coded SQL statements is not appealing, because of the dynamic nature of the queries being issued against the database server. Because of this sometimes there is a need to dynamically create a SQL statement on the fly and then run that command. This can be done quite simply from the application perspective where the statement is built on the fly whether you are using ASP.NET , ColdFusion or any other programming language. But how do you do this from within a SQL Server stored procedure? SQL Server offers a few ways of running a dynamically built SQL statement. These ways are: Writing a query with parameters Using EXEC Using sp_executesql Writing a query with parameters This first approach is pretty straightforward if you only need to pass parameters into the WHERE clause of your SQL statement. Let’s say we need to find all records from the Customers table where City = ‘London’. This can be done easily as the following example shows.
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Delete Duplicate rows from the table.

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Delete Duplicate rows from the table.
Suppose there is a table called "EmployeeTable" which have some duplicate records.
There is a three way to delete the duplicate rows.

First way to delete duplicate rows :


Select distinct * into Emp_Temp_Table from EmployeeTable

In the above line we are inserting all the distinct row of the "EmployeeTable" to another table "Emp_Temp_Table" (Emp_Temp_Table will create automatically when you use the above query.)
Actuall the above query create clone of EmployeeTable and insert all the distinct row inside the Clone Table (Emp_Temp_Table).


drop table EmployeeTable

sp_rename 'Emp_Temp_Table',EmployeeTable'

Then Delete the orginal table and rename the clone table with the name of orginal table.


Second way to delete duplicate rows :

Select distinct * into Emp_Temp_Table from EmployeeTable

Truncate table EmployeeTable

insert into EmployeeTable select * from Emp_Temp_Table

drop table Emp_Temp_Table


Third way to delete duplicate rows :

Populate the new Primary Key


Alter table EmployeeTable add NewPK int NULL
Go
Declare @intCounter int
Set @intCounter = 0
Update EmployeeTable
SET @intCounter = NewPK = @intCounter + 1

Select name,RecCount=count(*), PktoKeep = max(NewPK)
Into #dupes
From EmployeeTable
Group by name
Having count(*) > 1
Order by count(*) desc

Delete dupes except one Primary key for each dup record


Delete test
from EmployeeTable a join #dupes d
a.name
where a.NewPK not in (select PKtoKeep from #dupes)


Remove the NewPK column


ALTER TABLE test DROP COLUMN NewPK
go

drop table #dupes

Comments

Sapien said…
This is the best, no nonsense, and most simplistic answer I've seen so far. That one line created the table, with all the right columns for me, then I just renamed the old table and it's done. Thanks.
October 2, 2008 at 6:15 AM
rana said…
tahnks.
This is very good query.I have asked this question my time in interview.It very simple to remember.
February 17, 2011 at 11:15 PM
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