MySQL使用存储过程代替子查询

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• x220 笔记本 , cpu: i5-2520 , 磁盘intel ssd sata2接口 , 就是这么搓的环境 :(
• 源语句

select * from employees e inner join
(select emp_no ,count(*) from salaries group by emp_no) s
on s.emp_no = e.emp_no where e.emp_no between 10001 and 10010;

+----+-------------+------------+------------+-------+----------------+-------------+---------+--------------------+---------+----------+-------------+
| id | select_type | table      | partitions | type  | possible_keys  | key         | key_len | ref                | rows    | filtered | Extra       |
+----+-------------+------------+------------+-------+----------------+-------------+---------+--------------------+---------+----------+-------------+
         |   100.00 | Using where |
 | PRIMARY     | <derived2> | NULL       | ref   | <auto_key0>    | <auto_key0> | 4       | employees.e.emp_no |      10 |   100.00 | NULL        |
         |   100.00 | Using index |
+----+-------------+------------+------------+-------+----------------+-------------+---------+--------------------+---------+----------+-------------+

+--------+------------+------------+-----------+--------+------------+--------+----------+
| emp_no | birth_date | first_name | last_name | gender | hire_date  | emp_no | count(*) |
+--------+------------+------------+-----------+--------+------------+--------+----------+
     |
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+--------+------------+------------+-----------+--------+------------+--------+----------+
 rows in set (1.00 sec)

• 从id=2开始就先执行salaries 表的子查询 , 可以看出红色字部分是临时索引,从5.6开始就有这个功能,这个临时索引是在内存生成的,如果返回数据量大占用内存越多,表之间关联性能就下降,也有可能把内存涨满 , 最终用了1秒执行效率
• 现在想把这个salaries表的子查询跟employees表同一时间执行,并且达到性能效率提升
• 创建一个存储过程另外关联这个salaries表,如下:

create FUNCTION t1(in_emp_no int ) RETURNS INT
BEGIN
DECLARE a1 int ;
select count(*) into a1 from salaries where emp_no = in_emp_no group by emp_no;
RETURN a1;
end;

mysql  and t1(e.emp_no);
+----+-------------+-------+------------+-------+---------------+---------+---------+------+------+----------+-------------+
| id | select_type | table | partitions | type  | possible_keys | key     | key_len | ref  | rows | filtered | Extra       |
+----+-------------+-------+------------+-------+---------------+---------+---------+------+------+----------+-------------+
         |   100.00 | Using where |
+----+-------------+-------+------------+-------+---------------+---------+---------+------+------+----------+-------------+
 row  warning (0.00 sec)

• 变成了只有一个表运行,而salaries 和 employees 关联在另外一个线程执行存储过程, 至于怎样从mysql核心看它执行这个稍后揭晓 , 最终使用了0.01秒执行 , 记住这是5年前的x220哦

+--------+------------+------------+-----------+--------+------------+--------------+
| emp_no | birth_date | first_name | last_name | gender | hire_date  | t1(e.emp_no) |
+--------+------------+------------+-----------+--------+------------+--------------+
    |
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+--------+------------+------------+-----------+--------+------------+--------------+
 rows in set (0.01 sec)