Limiting Result Sets Using TOP and PERCENT

The TOP clause limits the number of rows returned in the result set.

TOP n [PERCENT]

n specifies how many rows are returned. If PERCENT is not specified, n is the number of rows to return. If PERCENT is specified, n is the percentage of the result set rows to return:

TOP 120 /*Return the top 120 rows of the result set. */

TOP 15 PERCENT /* Return the top 15% of the result set. */.

If a SELECT statement that includes TOP also has an ORDER BY clause, the rows to be returned are selected from the ordered result set. The entire result set is built in the specified order and the top n rows in the ordered result set are returned.

The other method of limiting the size of a result set is to execute a SET ROWCOUNT n statement before executing a statement. SET ROWCOUNT differs from TOP in these ways:

• The SET ROWCOUNT limit applies to building the rows in the result set before an ORDER BY is evaluated. Even if ORDER BY is specified, the SELECT statement is terminated when n rows have been selected. n rows are selected, then ordered and returned to the client.
• The TOP clause applies to the single SELECT statement in which it is specified. SET ROWCOUNT remains in effect until another SET ROWCOUNT statement is executed, such as SET ROWCOUNT 0 to turn the option off.

See Also