mysql哪些语句使用了索引呢

------为表中的字段增加默认值语法--

alter table account modify income int(10) not null default '0';

------mysql哪些语句使用了索引呢？

mysql> explain select * from account where income between 6000000 and 7000000;

+----+-------------+---------+------+---------------+------+---------+------+------+-------------+

| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |

+----+-------------+---------+------+---------------+------+---------+------+------+-------------+

| 1 | SIMPLE | account | ALL | income | NULL | NULL | NULL | 6 | Using where |

+----+-------------+---------+------+---------------+------+---------+------+------+-------------+

1 row in set (0.00 sec)

mysql> explain select * from account where income>6000000 and income<7000000;

+----+-------------+---------+-------+---------------+--------+---------+------+------+-----------------------+

| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |

+----+-------------+---------+-------+---------------+--------+---------+------+------+-----------------------+

| 1 | SIMPLE | account | range | income | income | 4 | NULL | 1 | Using index condition |

+----+-------------+---------+-------+---------------+--------+---------+------+------+-----------------------+

1 row in set (0.00 sec)

mysql> explain select * from account where income>6000000;

+----+-------------+---------+------+---------------+------+---------+------+------+-------------+

| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |

+----+-------------+---------+------+---------------+------+---------+------+------+-------------+

| 1 | SIMPLE | account | ALL | income | NULL | NULL | NULL | 6 | Using where |

+----+-------------+---------+------+---------------+------+---------+------+------+-------------+

1 row in set (0.00 sec)

mysql> explain select * from account where income>=6000000;

+----+-------------+---------+------+---------------+------+---------+------+------+-------------+

| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |

+----+-------------+---------+------+---------------+------+---------+------+------+-------------+

| 1 | SIMPLE | account | ALL | income | NULL | NULL | NULL | 6 | Using where |

+----+-------------+---------+------+---------------+------+---------+------+------+-------------+

1 row in set (0.00 sec)

mysql> explain select * from account where income<6000000;

+----+-------------+---------+-------+---------------+--------+---------+------+------+-----------------------+

| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |

+----+-------------+---------+-------+---------------+--------+---------+------+------+-----------------------+

| 1 | SIMPLE | account | range | income | income | 4 | NULL | 2 | Using index condition |

+----+-------------+---------+-------+---------------+--------+---------+------+------+-----------------------+

1 row in set (0.00 sec)

mysql> explain select * from account where income<=6000000;

+----+-------------+---------+------+---------------+------+---------+------+------+-------------+

| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |

+----+-------------+---------+------+---------------+------+---------+------+------+-------------+

| 1 | SIMPLE | account | ALL | income | NULL | NULL | NULL | 6 | Using where |

+----+-------------+---------+------+---------------+------+---------+------+------+-------------+

1 row in set (0.00 sec)

可以看出，使用<号使用了索引，

< and > 也使用了索引

=号用了索引