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.
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 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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