SQL HAVING

SQL HAVING

The SQL HAVING clause is used to restrict conditionally the output of a SQL statement, by a SQL aggregate function used in your SELECT list of columns.

You can't specify criteria in a SQL WHERE clause against a column in the SELECT list for which SQL aggregate function is used. For example the following SQL statement will generate an error:


SELECT Employee, SUM (Hours)
FROM EmployeeHours
WHERE SUM (Hours) > 24
GROUP BY Employee


The SQL HAVING clause is used to do exactly this, to specify a condition for an aggregate function which is used in your query:


SELECT Employee, SUM (Hours)
FROM EmployeeHours
GROUP BY Employee
HAVING SUM (Hours) > 24



The above SQL statement will select all employees and the sum of their respective hours, as long as this sum is greater than 24. The result of the SQL

Socurce : http://www.sql-tutorial.net