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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what Is Cursor

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The basic syntax of a cursor is:

DECLARE @AuthorID char(11)
 
DECLARE c1 CURSOR READ_ONLY
FOR
SELECT au_id
FROM authors

OPEN c1

FETCH NEXT FROM c1
INTO @AuthorID

WHILE @@FETCH_STATUS = 0
BEGIN

 PRINT @AuthorID

 FETCH NEXT FROM c1
 INTO @AuthorID

END

CLOSE c1
DEALLOCATE c1

The DECLARE CURSOR statement defines the SELECT statement that forms the basis of the cursor. You can do just about anything here that you can do in a SELECT statement. The OPEN statement statement executes the SELECT statement and populates the result set. The FETCH statement returns a row from the result set into the variable. You can select multiple columns and return them into multiple variables. The variable @@FETCH_STATUS is used to determine if there are any more rows. It will contain 0 as long as there are more rows. We use a WHILE loop to move through each row of the result set.

The READ_ONLY clause is important in the code sample above. That dramatically improves the performance of the cursor.

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