MySQL的查询缓存机制（2）_MySQL

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　　+---------------+-------+
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)