Just as the WHERE clause limits the number of rows retrieved by the SELECT statement, the HAVING clause limits the number of groups retrieved for the GROUP BY clause.

                         SELECT      [ALL | DISTINCT]
                                           [* | column1[, column2, ...]]
                            FROM      [table1 correlation, ...
                                          | view1 correlation, ...]
                          WHERE       condition1[, condition2, ...]
                          GROUP BY  column1[, column2, ...]
                         HAVING      condition1[, condition2, ...]
                           ORDER BY column1 [ASC | DESC][, column2 [ASC | DESC], …];

> Unlike the WHERE clause, the HAVING clause can contain a column function.

> The HAVING clause comes after the GROUP BY clause and before the ORDER BY clause.

> The WHERE clause can eliminate data from consideration by the GROUP BY clause. The WHERE clause is applied before grouping happens. The HAVING clause is applied after grouping happens.

> An entry in the HAVING clause must match an entry in the SELECT statement or be a column function.
> Column names in the HAVING clause do not have to be in the same order as the SELECT statement.

> If the SELECTed name is qualified, the HAVING name must be qualified.

> An expression in the HAVING clause must match the exact same expression in the SELECT statement.

> Multiple HAVING conditions can be specified using AND, OR, and NOT.