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)