Skip to Main Content
MySQL Cookbook
book

MySQL Cookbook

by Paul DuBois
October 2002
Intermediate to advanced content levelIntermediate to advanced
1024 pages
27h 26m
English
O'Reilly Media, Inc.
Content preview from MySQL Cookbook

Finding Smallest or Largest Summary Values

Problem

You want to compute per-group summary values, but display only the smallest or largest of them.

Solution

Add a LIMIT clause to the query.

Discussion

MIN( ) and MAX( ) find the values at the endpoints of a range of values, but if you want to know the extremes of a set of summary values, those functions won’t work. The arguments to MIN( ) and MAX( ) cannot be other aggregate functions. For example, you can easily find per-driver mileage totals:

mysql> SELECT name, SUM(miles)
    -> FROM driver_log
    -> GROUP BY name;
+-------+------------+
| name  | SUM(miles) |
+-------+------------+
| Ben   |        362 |
| Henry |        911 |
| Suzi  |        893 |
+-------+------------+

But to select only the record for the driver with the most miles, this doesn’t work:

mysql> SELECT name, SUM(miles)
    -> FROM driver_log
    -> GROUP BY name
    -> HAVING SUM(miles) = MAX(SUM(miles));
ERROR 1111 at line 1: Invalid use of group function

Instead, order the rows with the largest SUM( ) values first and use LIMIT to select the first record:

mysql> SELECT name, SUM(miles) AS 'total miles'
    -> FROM driver_log
    -> GROUP BY name
    -> ORDER BY 'total miles' DESC LIMIT 1;
+-------+-------------+
| name  | total miles |
+-------+-------------+
| Henry |         911 |
+-------+-------------+

An alias is used in the ORDER BY clause because ORDER BY cannot refer directly to aggregate functions, as discussed earlier in Recipe 7.14.

Note that if there is more than one row with the given summary value, this type of query ...

Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
and much more.
Start your free trial

You might also like

MySQL Reference Manual

MySQL Reference Manual

Michael Widenius, David Axmark, Kaj Arno
High Performance MySQL

High Performance MySQL

Jeremy D. Zawodny, Derek J. Balling
MySQL Stored Procedure Programming

MySQL Stored Procedure Programming

Guy Harrison, Steven Feuerstein

Publisher Resources

ISBN: 0596001452Catalog PageErrata