SELECT * FROM a LEFT JOIN b ON a.aID = b.bID;
a为主，a的数据全显示，连不上b的对应字段为空
SELECT * FROM a RIGHT JOIN b ON a.aID = b.bID;
b为主，b的数据全显示，连不上a的对应字段为空
SELECT * FROM a INNER JOIN a ON a.aID = b.bID; 相当于where
a.aID=b.bID
mysql的join,布布扣,bubuko.com
mysql的join
原文：http://www.cnblogs.com/consume/p/3655525.html
