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 ...
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