left jion附件有问题为什么？

SELECT a.*,b.quan1 from `user` a,
(SELECT * FROM user_main  t1 WHERE t1.`name`="dsdad")  b 
WHERE 
a LEFT JOIN b --这行这里报错，为什么呢？
ON a.id=b.id

SELECT a.*,b.quan1 from `user` a LEFT JOIN (SELECT * FROM user_main  t1 WHERE t1.`name`='dsdad')  b ON a.id=b.id

LEFT JOIN不能当做where条件，你都from两张表了还用left join明显多于，你这么写直接where 后面跟a.id=b.id就行了，或者

SELECT a.*,b.quan1 from `user` a
LEFT JOIN user_main  b
ON a.id=b.id
and b.`name`="dsdad"