SQL语句优化问题

版权声明：本文为博主原创文章，未经博主允许不得转载。 https://blog.csdn.net/bug_love/article/details/79051551

有时返回数据时，需要有三张或以上的表需要查询。一张表的数据往往需要连接多张。效率非常的差。

SELECT
	user.id,
	user.uuid,
	user.user_name AS username,
	user.login_name name,
	user.sex,
	user.phone,
	(
		SELECT
			group_concat(NAME)
		FROM
			qx_menu
		WHERE
			CONCAT(',',user.LEVEL,',') LIKE CONCAT('%,',uuid,',%')
	) AS level,
group_concat(site.`name`) as siteStrs
FROM
	sys_user user
LEFT JOIN qx_user2site us ON us.user_id = user.uuid
LEFT JOIN dt_site site ON us.site_id = site.uuid AND site.isvalid = 1
WHERE
	(1 = 1)
AND user.isvalid = 1 
GROUP BY `user`.id
LIMIT 0, 15