MySQL Cookbook

Sorting by Fixed-Length Substrings

Problem

You want to sort using parts of a column that occur at a given position within the column.

Solution

Pull out the parts you need with LEFT( ), MID( ), or RIGHT( ) and sort them.

Discussion

Suppose you have a housewares table that acts as a catalog for houseware furnishings, and that items are identified by 11-character ID values consisting of three subparts: a three-character category abbreviation (such as DIN for “dining room” or KIT for “kitchen”), a five-digit serial number, and a two-character country code indicating where the part is manufactured:

mysql> SELECT * FROM housewares;
+------------+------------------+
| id         | description      |
+------------+------------------+
| DIN40672US | dining table     |
| KIT00372UK | garbage disposal |
| KIT01729JP | microwave oven   |
| BED00038SG | bedside lamp     |
| BTH00485US | shower stall     |
| BTH00415JP | lavatory         |
+------------+------------------+

This is not necessarily a good way to store complex ID values, and later we’ll consider how to represent them using separate columns (Recipe 11.14). But for now, assume that the values must be stored as just shown.

If you want to sort records from this table based on the id values, you’d just use the entire column value:

mysql> SELECT * FROM housewares ORDER BY id; +------------+------------------+ | id | description | +------------+------------------+ | BED00038SG | bedside lamp | | BTH00415JP | lavatory | | BTH00485US | shower stall | | DIN40672US | dining table ...