mysql的sql性能分析器(3)

12 rows in set (0.03 sec)
 
mysql> show profile for query 8;
+--------------------+----------+
| Status             | Duration |
+--------------------+----------+
| (initialization)   | 0.000064 |
| Opening tables     | 0.000018 |
| System lock        | 0.00001  |
| Table lock         | 0.000013 |
| init               | 0.00002  |
| optimizing         | 0.00001  |
| executing          | 0.002589 |
| end                | 0.000459 |
| query end          | 0.000007 |
| freeing items      | 0.000015 |
| closing tables     | 0.000012 |
| logging slow query | 0.000005 |
+--------------------+----------+
12 rows in set (0.00 sec)
 
mysql> select sum(format(duration,6)) as duration from information_schema.profiling where query_id=7;
+----------+
| duration |
+----------+
| 0.003688 |
+----------+
1 row in set (0.02 sec)
 
mysql> select sum(format(duration,6)) as duration from information_schema.profiling where query_id=8;
+----------+
| duration |
+----------+
| 0.003222 |
+----------+
1 row in set (0.00 sec)
 
mysql>
 
从如上的信息可以看出这两个sql的profile统计信息里，前4项差别比较大，这是两个sql主要区别，第二次查询有很多
缓存了了。SQL 性能分析器可以帮助我们对一些比较难以确定性能问题的SQL 进行诊断，找出问题根源。
 
 
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