Mysql Explain Ïê½â
Mysql Explain Ïê½â
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explain < table_name >
ÀýÈç: explain select * from t3 where id=3952602;
¶þ.explainÊä³ö½âÊÍ
+----+-------------+-------+-------+-------------------+---------+---------+-------+------+-------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+-------+-------+-------------------+---------+---------+-------+------+-------+
1.id
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ÀýÈç:
mysql> explain select * from (select * from ( select * from t3 where id=3952602) a) b;
+----+-------------+------------+--------+-------------------+---------+---------+------+------+-------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+------------+--------+-------------------+---------+---------+------+------+-------+
| 1 | PRIMARY | <derived2> | system | NULL | NULL | NULL | NULL | 1 | |
| 2 | DERIVED | <derived3> | system | NULL | NULL | NULL | NULL | 1 | |
| 3 | DERIVED | t3 | const | PRIMARY,idx_t3_id | PRIMARY | 4 | | 1 | |
+----+-------------+------------+--------+-------------------+---------+---------+------+------+------
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MYSQL ɾ³ýͬһ±íÖÐÖØ¸´¼Ç¼
CREATE TABLE `user` (
`db_id` varchar(255) NOT NULL,
`name` varchar(45) default NULL,
`age` int(10) unsigned NOT NULL,
`address` varchar(45) default NULL,
PRIMARY KEY (`db_id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
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http://www.xiaojb.com/archives/it/mysqlroot.shtml
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