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//表结构
CREATE TABLE IF NOT EXISTS `radacct` (
`RadAcctId` bigint(21) NOT NULL AUTO_INCREMENT,
`UserName` varchar(64) NOT NULL DEFAULT '',
`AcctSessionTime` int(12) DEFAULT NULL,
`AcctInputOctets` bigint(12) DEFAULT NULL,
`AcctOutputOctets` bigint(12) DEFAULT NULL,
...
......
PRIMARY KEY (`RadAcctId`),
KEY `UserName` (`UserName`),
KEY `AcctSessionTime` (`AcctSessionTime`),
KEY `AcctInputOctets` (`AcctInputOctets`),
KEY `AcctOutputOctets` (`AcctOutputOctets`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci AUTO_INCREMENT=456017;
$sql = 'SELECT UserName, count(*) AS numOfSession, sum(AcctSessionTime) AS Time, sum(AcctInputOctets) AS Upload, sum(AcctOutputOctets) AS Download, sum(AcctInputOctets+AcctOutputOctets) AS Bandwidth FROM radacct GROUP BY UserName';
mysql> explain SELECT UserName, count(*) AS numOfSession, sum( AcctSessionTime ) AS Time, sum( AcctInputOctets ) AS Upload, sum( AcctOutputOctets ) AS Download, sum( AcctInputOctets + AcctOutputOctets ) AS Bandwidth FROM radacct GROUP BY UserName;
+----+-------------+---------+------+---------------+------+---------+------+--------+---------------------------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+---------+------+---------------+------+---------+------+--------+---------------------------------+
| 1 | SIMPLE | radacct | ALL | NULL | NULL | NULL | NULL | 456010 | Using temporary; Using filesort |
+----+-------------+---------+------+---------------+------+---------+------+--------+---------------------------------+
mysql> EXPLAIN SELECT UserName, count( * ) AS numOfSession, sum( AcctSessionTime ) AS Time FROM radacct FORCE INDEX ( `UserName` ) GROUP BY UserName;
+----+-------------+---------+-------+---------------+----------+---------+------+--------+-------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+---------+-------+---------------+----------+---------+------+--------+-------+
| 1 | SIMPLE | radacct | index | NULL | UserName | 66 | NULL | 456010 | |
+----+-------------+---------+-------+---------------+----------+---------+------+--------+-------+
+----+-------------+----------+-------+---------------+----------+---------+------+--------+-------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+----------+-------+---------------+----------+---------+------+--------+-------+
| 1 | SIMPLE | UserName | index | NULL | UserName | 66 | NULL | 456010 | |
+----+-------------+----------+-------+---------------+----------+---------+------+--------+-------+