MySQL两表联查，三表联查

两表联查

SELECT A. * , B. * 
FROM memberdata A LEFT JOIN members B ON A.uid = B.uid
WHERE 1 
LIMIT 0 , 30

三表

SELECT * FROM tx1 left join (tx2, tx3) ON (tx1.id=tx2.tid ANDtx2.tid=tx3.tid) where tx1.id = 3

三表查询(只需有两个表有数据即可输出数据)

select * from content as c inner join extra as e on c.id=e.cid leftjoin images as i on c.id=i.cid