[code="sql"]
EXPLAIN SELECT * FROM products p JOIN
(SELECT * FROM synchronization WHERE time_flag > 0 AND sys_type='products') s
ON p.product_code = s.sys_id;
EXPLAIN SELECT * FROM products p JOIN synchronization s ON p.product_code = s.sys_id WHERE s.time_flag > 0 AND s.sys_type='products';
[/code]
请问mysql中上面两句sql哪个效率更高啊,我使用explain 查看如下图,看不出来谁效率高,希望哪位帮忙解说下,非常感谢!