The following example shows the use of HAVING as applied to the aggregate results of a single group defined in the SELECT list, which is particularly useful in a SELECT subquery.
SELECT COUNT(employee) FROM department WHERE dept_no = 100 HAVING COUNT(employee) > 10;
The following SELECT statements are additional examples of the correct use of the HAVING clause.
SELECT SUM(t.a) FROM t,u HAVING SUM(t.a)=SUM(u.a); SELECT SUM(t.a), SUM(u.a) FROM t,u HAVING SUM(t.b)=SUM(u.b); SELECT SUM(t.a) FROM t,u HAVING SUM(t.b)=SUM(u.b) AND u.b = 1 GROUP BY u.b;