mysql 索引对于select速度提升作用实验

说明；News2在News的基础上把is_active加上索引。

mysql> select count(*) from News2 where is_active=1;

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

| count(*) |

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

|  7820331 |

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

1 row in set (14.77 sec)





mysql> select count(*) from News2 where is_active=0;

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

| count(*) |

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

|  7797380 |

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

1 row in set (14.56 sec)





mysql> select count(*) from News where is_active=0;

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

| count(*) |

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

|  7797380 |

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

1 row in set (35.20 sec)





mysql> select count(*) from News where is_active=1;

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

| count(*) |

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

|  7820331 |

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

1 row in set (35.12 sec)