Section 7.0. Introduction

7.0. Introduction

This chapter covers sorting, an operation that is extremely important for controlling how MySQL displays results from SELECT statements. Sorting is performed by adding an ORDER BY clause to a query. Without such a clause, MySQL is free to return rows in any order, so sorting helps bring order to disorder and makes query results easier to examine and understand. (Sorting is also performed implicitly when you use a GROUP BY clause, as discussed in Section 8.13.)

You can sort rows of a query result several ways:

• Using a single column, a combination of columns, or even parts of columns

• Using ascending or descending order

• Using the result of an expression

• Using case-sensitive or case-insensitive string comparisons

• Using temporal ordering

The driver_log table is used for several examples in this chapter; it contains columns for recording daily mileage logs for a set of truck drivers:

mysql> SELECT * FROM driver_log; +--------+-------+------------+-------+ | rec_id | name  | trav_date  | miles | +--------+-------+------------+-------+ |      1 | Ben   | 2006-08-30 |   152 | |      2 | Suzi  | 2006-08-29 |   391 | |      3 | Henry | 2006-08-29 |   300 | |      4 | Henry | 2006-08-27 |    96 | |      5 | Ben   | 2006-08-29 |   131 | |      6 | Henry | 2006-08-26 |   115 | |      7 | Suzi  | 2006-09-02 |   502 | |      8 | Henry | 2006-09-01 |   197 | |      9 | Ben   | 2006-09-02 |    79 | |     10 | Henry | 2006-08-30 |   203 | +--------+-------+------------+-------+ 

Many other examples use the mail table (used in earlier chapters):

mysql> SELECT * FROM mail; +---------------------+---------+---------+---------+---------+---------+ | t                   | srcuser | srchost | dstuser | dsthost | size    | +---------------------+---------+---------+---------+---------+---------+ | 2006-05-11 10:15:08 | barb    | saturn  | tricia  | mars    |   58274 | | 2006-05-12 12:48:13 | tricia  | mars    | gene    | venus   |  194925 | | 2006-05-12 15:02:49 | phil    | mars    | phil    | saturn  |    1048 | | 2006-05-13 13:59:18 | barb    | saturn  | tricia  | venus   |     271 | | 2006-05-14 09:31:37 | gene    | venus   | barb    | mars    |    2291 | | 2006-05-14 11:52:17 | phil    | mars    | tricia  | saturn  |    5781 | | 2006-05-14 14:42:21 | barb    | venus   | barb    | venus   |   98151 | | 2006-05-14 17:03:01 | tricia  | saturn  | phil    | venus   | 2394482 | | 2006-05-15 07:17:48 | gene    | mars    | gene    | saturn  |    3824 | | 2006-05-15 08:50:57 | phil    | venus   | phil    | venus   |     978 | | 2006-05-15 10:25:52 | gene    | mars    | tricia  | saturn  |  998532 | | 2006-05-15 17:35:31 | gene    | saturn  | gene    | mars    |    3856 | | 2006-05-16 09:00:28 | gene    | venus   | barb    | mars    |     613 | | 2006-05-16 23:04:19 | phil    | venus   | barb    | venus   |   10294 | | 2006-05-17 12:49:23 | phil    | mars    | tricia  | saturn  |     873 | | 2006-05-19 22:21:51 | gene    | saturn  | gene    | venus   |   23992 | +---------------------+---------+---------+---------+---------+---------+ 

Other tables are used occasionally as well. You can create most of them with scripts found in the tables directory of the recipes distribution.