Why is it that a field name that works fine for a JOIN is invalid in a
STRAIGHT JOIN?
mysql> show create table fldsndm;
+---------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Table | Create Table |
+---------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| fldsndm | CREATE TABLE `fldsndm` (
`p` varchar(200) NOT NULL,
`cd` datetime NOT NULL,
`cms` smallint(6) NOT NULL,
`pip` char(15) NOT NULL,
`pport` smallint(6) NOT NULL,
`pboot` bigint(20) NOT NULL,
`msgid` bigint(20) NOT NULL,
`startgtime` bigint(20) NOT NULL,
`datalen` int(11) NOT NULL,
`toself` tinyint(1) DEFAULT NULL,
`sepoch` bigint(20) NOT NULL DEFAULT '0',
`c` decimal(11,3) NOT NULL DEFAULT '0.000',
UNIQUE KEY `pbm` (`p`,`pboot`,`msgid`)
) ENGINE=MEMORY DEFAULT CHARSET=latin1 |
+---------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)
mysql> show create table fldrcv;
+--------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Table | Create Table |
+--------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| fldrcv | CREATE TABLE `fldrcv` (
`p` varchar(200) NOT NULL,
`cd` datetime NOT NULL,
`cms` smallint(6) NOT NULL,
`pip` char(15) NOT NULL,
`pport` smallint(6) NOT NULL,
`pboot` bigint(20) DEFAULT NULL,
`qip` char(15) NOT NULL,
`qport` smallint(6) NOT NULL,
`qboot` bigint(20) DEFAULT NULL,
`msgid` bigint(20) NOT NULL,
`startgtime` bigint(20) NOT NULL,
`datalen` int(11) NOT NULL,
`q` varchar(200) DEFAULT NULL,
`repoch` bigint(20) NOT NULL DEFAULT '0',
`c` decimal(11,3) NOT NULL DEFAULT '0.000',
KEY `c` (`c`),
KEY `pec` (`p`,`repoch`,`c`),
KEY `peqms` (`p`,`repoch`,`q`,`msgid`,`startgtime`),
KEY `qbm` (`q`,`qboot`,`msgid`),
KEY `pbm` (`p`,`pboot`,`msgid`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1 |
+--------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)
mysql> explain extended select * from fldrcv join fldsndm on
(fldrcv.q=fldsndm.p AND fldrcv.qboot=fldsndm.pboot and
fldrcv.msgid=fldsndm.msgid);
+----+-------------+---------+------+---------------+------+---------+---------------------------------------------------------------------------------------------+-------+----------+-------------+
| id | select_type | table | type | possible_keys | key | key_len | ref
| rows | filtered | Extra |
+----+-------------+---------+------+---------------+------+---------+---------------------------------------------------------------------------------------------+-------+----------+-------------+
| 1 | SIMPLE | fldsndm | ALL | pbm | NULL | NULL |
NULL | 29036 | 100.00 | |
| 1 | SIMPLE | fldrcv | ref | qbm | qbm | 220 |
bigCell2906_flood.fldsndm.p,bigCell2906_flood.fldsndm.pboot,bigCell2906_flood.fldsndm.msgid
| 452 | 100.00 | Using where |
+----+-------------+---------+------+---------------+------+---------+---------------------------------------------------------------------------------------------+-------+----------+-------------+
2 rows in set, 1 warning (0.00 sec)
mysql> explain extended select * from fldrcv straight join fldsndm on
(fldrcv.q=fldsndm.p AND fldrcv.qboot=fldsndm.pboot and
fldrcv.msgid=fldsndm.msgid);
ERROR 1054 (42S22): Unknown column 'fldrcv.q' in 'on clause'
mysql>
Thanks,
Mike Spreitzer
