例子1：SELECT * FROM contact_card AS c
INNER JOIN contact_card_extend AS b ON c.uuid = b.uuid AND c.uuid='AX61t09bpcmmhsXISvbAv1mdb71JZwt3' AND c.status='active'
INNER JOIN contact_card_vcardinfo AS info ON c.uuid=info.card_id；
例子2：SELECT * FROM contact_card AS c
INNER JOIN contact_card_extend AS b ON c.uuid = b.uuid
INNER JOIN contact_card_vcardinfo AS info ON c.uuid=info.card_id
WHERE c.uuid='AX61t09bpcmmhsXISvbAv1mdb71JZwt3' AND c.status='active'
回复讨论(解决方案)
两者一样
不过一般都写成后者，因为 c.uuid='AX61t09bpcmmhsXISvbAv1mdb71JZwt3' AND c.status='active' 与连接无关
两者一样
不过一般都写成后者，因为 c.uuid='AX61t09bpcmmhsXISvbAv1mdb71JZwt3' AND c.status='active' 与连接无关
就是这样子
就大数据来说不知道前者是不是更快点，就理论来说前者是先通过第一个查询的出的结果来进行关联，而第一个查询已经进行了条件筛选，所以应该是要比第二个所有查询关联完之后再进行条件筛选快。我想应该是这样没有试所以就来问问。
那只是你的想象而已
数据库中有一个专门用来解析 join 命令的过程，解析时对于与连接无关的表达式都剔出来放到 where 子句中
如果你只想让主表符合条件的记录参与查询，应使用子查询
SELECT * FROM
(select * from contact_card where uuid='AX61t09bpcmmhsXISvbAv1mdb71JZwt3' AND status='active') AS c
INNER JOIN contact_card_extend AS b ON c.uuid = b.uuid
INNER JOIN contact_card_vcardinfo AS info ON c.uuid=info.card_id
受教了，谢谢大神儿！已经改正错误！