TOP and SET ROWCOUNT are both valid methods of limiting the result sets from a query. They are however very different commands. The TOP clause of a command limits that single command, while the SET ROWCOUNT command limits all eligible queries within the connection until another SET ROWCOUNT is called.
SET ROWCOUNT 10
SELECT * FROM CITY ORDER BY CITY_NAME
SELECT * FROM STATE ORDER BY STATE_CD
SET ROWCOUNT 0
Returns first 10 records from CITY table as well as 10 records from STATE table.
The equivalent code for the above using TOP n clause is as follows:
SELECT TOP 10 * FROM CITY ORDER BY CITY_NAME
SELECT TOP 10 * FROM STATE ORDER BY STATE_CD