sql话语学习

sql语句学习
SELECT * FROM t_pic_OnlinePictureGroupTag a LEFT JOIN
t_pic_OnlinePictureTagLib b
ON a.onlinepicturetaglibid=b.tid
LEFT JOIN t_pic_OnlinePictureGroup c
ON a.onlinepicturegroupid=c.id
WHERE CODE IN ('a1','b1')