在mysql查询时最好不要发生类型转换,如把varchar转换成int
mysql> explain select * from user where name=1\G
//如果你确定name字段是整型就不要把它转化成字符串,不加单引号
*************************** 1. row ***************************
id: 1
select_type: SIMPLE
table: user
type: ALL
possible_keys: index_name_password
key: NULL
key_len: NULL
ref: NULL
rows: 99727
Extra: Using where
1 row in set (0.02 sec)
mysql> explain select * from user where name='1'\G
//如果你确定name字段是字符串就不要把它转化成整型,加单引号
*************************** 1. row ***************************
id: 1
select_type: SIMPLE
table: user
type: ref
possible_keys: index_name_password
key: index_name_password
key_len: 111
ref: const
rows: 1
Extra: Using where
1 row in set (0.00 sec)