MySQL的查询缓存机制（2）_MySQL

　　+---------------+-------+
8 rows in set (0.00 sec)

mysql> select count(*) from animals;
+----------+
| count(*) |
+----------+
| 6 |
+----------+
1 row in set (0.00 sec)

mysql> SHOW STATUS LIKE ’Qcache%’;
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| Qcache_hits | 1 | --表示sql在缓存中直接得到结果，不需要再去解析
+---------------+-------+
8 rows in set (0.00 sec)

mysql> select count(*) from animals;
+----------+
| count(*) |
+----------+
| 6 |
+----------+
1 row in set (0.00 sec)

mysql> select count(*) from animals;
+----------+
| count(*) |
+----------+
| 6 |
+----------+
1 row in set (0.00 sec)

mysql> SHOW STATUS LIKE ’Qcache_hits’;
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| Qcache_hits | 3 | --上面的sql也是是从缓存中直接取到结果
+---------------+-------+
1 row in set (0.00 sec)

mysql> insert into animals select 9,’testsds’ ; --插入数据后，跟这个表所有相关的sql缓存就会被清空掉
Query OK, 1 row affected (0.00 sec)
Records: 1 Duplicates: 0 Warnings: 0

mysql> select count(*) from animals;
+----------+
| count(*) |
+----------+
| 7 |
+----------+
1 row in set (0.00 sec)

mysql> SHOW STATUS LIKE ’Qcache_hits’;
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| Qcache_hits | 3 | --还是等于3，说明上一条sql是没有直接从缓存中直接得到的
+---------------+-------+
1 row in set (0.00 sec)

mysql> select count(*) from animals;
+----------+
| count(*) |
+----------+
| 7 |
+----------+
1 row in set (0.00 sec)

mysql> SHOW STATUS LIKE ’Qcache_hits’;
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| Qcache_hits | 4 |
+---------------+-------+
1 row in set (0.00 sec)