Monday, February 1, 2010

Sql Difference between where clause and Having clause

Hi, below are differences between where clause and having clause in mysql select statements.

1. Having clause is usually used with Group By clause although it can be used without it too.
2. 'Having' is just an additional filter to 'Where' clause.
3. 'Where' clause applies to the individual rows whereas 'Having' clause is used to test some condition on the group(usually aggregate methods) rather than on individual rows.
4. WHERE clause is used to impose condition on SELECT statement as well as single row function and is used before GROUP BY clause where as HAVING clause is used to impose condition on GROUP Function and is used after GROUP BY clause in the query. For example queries look at