----- Original Message -----
From: "pina-netc" <pina@stripped>
To: <mysql@stripped>
Sent: Saturday, December 04, 1999 10:23 PM
Subject: Index names in Where Clauses
> Does someone know if there is any way to make a select
> statment with an index name in the where clause, composed
> with more than one columns.
>
>Best regards, and thanks a lot.
The manual describes multi-column _indexes_, but I'm guessing that maybe
isn't what you want.
Are you trying to ORDER BY the combination of two columns (see below)?
Just guessing,
-Jay J
mysql> CREATE table foo ( id INT UNSIGNED PRIMARY KEY AUTO_INCREMENT, col_a
CHAR(10), col_b CHAR(10));
Query OK, 0 rows affected (0.23 sec)
mysql> INSERT INTO foo VALUES (null, 'a', 'a'), (null, 'a', 'b'), (null,
'b', 'a'), (null, 'b', 'b');
Query OK, 4 rows affected (0.18 sec)
Records: 4 Duplicates: 0 Warnings: 0
mysql> explain foo;
+-------+------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-------+------------------+------+-----+---------+----------------+
| id | int(10) unsigned | | PRI | 0 | auto_increment |
| col_a | char(10) | YES | | NULL | |
| col_b | char(10) | YES | | NULL | |
+-------+------------------+------+-----+---------+----------------+
3 rows in set (0.04 sec)
mysql> SELECT id, col_a, col_b, CONCAT(col_a, col_b) as OB FROM foo ORDER BY
OB desc;
+----+-------+-------+------+
| id | col_a | col_b | OB |
+----+-------+-------+------+
| 4 | b | b | bb |
| 3 | b | a | ba |
| 2 | a | b | ab |
| 1 | a | a | aa |
+----+-------+-------+------+
4 rows in set (0.20 sec)
mysql> SELECT id, col_a, col_b, CONCAT(col_a, col_b) as OB FROM foo ORDER BY
OB ASC;
+----+-------+-------+------+
| id | col_a | col_b | OB |
+----+-------+-------+------+
| 1 | a | a | aa |
| 2 | a | b | ab |
| 3 | b | a | ba |
| 4 | b | b | bb |
+----+-------+-------+------+
4 rows in set (0.01 sec)
