Restrict the number of rows affected in SQL Server

Introduction:

In my previous article I have explained about  how to Get number of affected rows in sql. In  this article I will explain about how to restrict the number of rows affected in  sql server.

Explanation:

To restrict the number of rows affected by sql server  SET ROWCOUNT is used. It Causes SQL Server to stop processing the query after the specified number of rows are returned.

Syntax:

SET ROWCOUNT { number | @number_var }

Arguments:

number | @number_var

Is the number, an integer, of rows to be processed before stopping the specific query.

The setting of the SET ROWCOUNT option is ignored for INSERT, UPDATE, and DELETE statements against remote tables and local and remote partitioned views.

To set this option off so that all rows are returned, specify SET ROWCOUNT 0

Setting the SET ROWCOUNT option causes most Transact-SQL statements to stop processing when they have been affected by the specified number of rows. This includes triggers and data modification statements such as INSERT, UPDATE, and DELETE. The ROWCOUNT option does not affect dynamic cursors, but it does limit the rowset of keyset and insensitive cursors. This option should be used with caution and primarily with the SELECT statement.

SET ROWCOUNT overrides the SELECT statement TOP keyword if the rowcount is the smaller value.

SET ROWCOUNT is ignored in INSERT, UPDATE, and DELETE statements when an explicit TOP expression is used in the same statement. This includes statements in which INSERT is followed by a SELECT clause.

The setting of SET ROWCOUNT is set at execute or run time and not at parse time.

Examples:

SET ROWCOUNT stops processing after the specified number of rows. In the following example, note that 545 rows meet the criteria of Quantity less than 300. However, from the number of rows returned by the update, you can see that not all rows were processed. ROWCOUNT affects all Transact-SQL statements.

USE AdventureWorks;

GO

SELECT count(*) AS Count

FROM Production.ProductInventory

WHERE Quantity < 300;

GO

Here is the result set.

Count       

----------- 

537          

(1 row(s) affected)

Now, set ROWCOUNT to 4 and update all rows with a Quantity less than 300.

SET ROWCOUNT 4;

UPDATE Production.ProductInventory

SET Quantity = 400

WHERE Quantity < 300;

GO

(4 row(s) affected)

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