Specify Conditions for Groups

You can limit the groups that appear in a query by specifying a condition that applies to groups as a whole — a HAVING clause. After the data has been grouped and aggregated, the conditions in the HAVING clause are applied. Only the groups that meet the conditions appear in the query.

For example, you might want to see the average price of all books for each publisher in a titles table, but only if the average price exceeds $10.00. In that case, you could specify a HAVING clause with a condition such as AVG(price) > 10.

Note   In some instances, you might want to exclude individual rows from groups before applying a condition to groups as a whole.

You can create complex conditions for a HAVING clause by using AND and OR to link conditions.

1. Specify the groups for your query.
2. If it is not already in the Grid pane, add the column on which you want to base the condition. (Most often the condition involves a column that is already a group or summary column.) You cannot use a column that is not part of an aggregate function or of the GROUP BY clause.
3. In the Criteria column, specify the condition to apply to the group.

   The Query Designer automatically creates a HAVING clause in the statement in the SQL pane, such as in the following example:

   SELECT pub_id, AVG(price)
   FROM titles
   GROUP BY pub_id
   HAVING (AVG(price) > 10)

4. Repeat steps 2 and 3 for each additional condition you want to specify.