前言
一些小技巧，可以帮助我们解决很多麻烦的事情。
更新自身表
UPDATE `table_a` SET `table_a`.`key` = ‘name’ WHERE `table_a`.`key` IN (SELECT b.`key` FROM `table_a` AS a JOIN `table_b` AS b ON a.`key` = b.`key`);
然而，MySQL并不支持，所以可以换另外一种。
UPDATE `table_a` AS a JOIN (SELECT b.`key` FROM `table_a` AS a JOIN `table_b` AS b ON a.`key` = b.`key`) AS b ON a.`key` = b.`key` SET a.`key` = ‘name’;
优化子查询：
使用JOIN语句来优化。
使用聚合查询
暂无好的想法~
-- EOF --
本文转载自IMJCW
原文链接：JOIN使用技巧
