Mysql Union实例

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前提，是每个查询结果集的列数要一样，类型要一样

SELECT g.goods_id FROM ( SELECT gr.`GOODS_ID`,COUNT(gr.`GOODS_ID`) num FROM rkgl_goods_repertory gr JOIN rkgl_repertory r ON r.`ID`=gr.`REPERTORY_ID` JOIN spgl_goods g ON g.`ID`=gr.`GOODS_ID` JOIN spgl_brand b ON b.`ID`=g.`BRAND_ID` JOIN spgl_goods_type gt ON gt.`ID`=g.`GOODS_TYPE_ID` WHERE r.`USER_ID`=36 AND g.`IS_DELETE`=FALSE AND gt.`IS_DELETE`=FALSE AND b.`IS_DELETE`=FALSE AND gr.`NUM`=0 GROUP BY gr.`GOODS_ID`) g WHERE g.num>1 UNION SELECT g.goods_id FROM ( SELECT gr.`GOODS_ID`,COUNT(gr.`GOODS_ID`) num FROM rkgl_goods_repertory gr JOIN rkgl_repertory r ON r.`ID`=gr.`REPERTORY_ID` JOIN spgl_goods g ON g.`ID`=gr.`GOODS_ID` JOIN spgl_brand b ON b.`ID`=g.`BRAND_ID` JOIN spgl_goods_type gt ON gt.`ID`=g.`GOODS_TYPE_ID` WHERE r.`USER_ID`=36 AND g.`IS_DELETE`=FALSE AND gt.`IS_DELETE`=FALSE AND b.`IS_DELETE`=FALSE AND gr.`NUM`=0 GROUP BY gr.`GOODS_ID`) g WHERE g.num=1

简单的实例就是

select * from a union select * from b

或者

(select * from a join b on a.id=b.a_id ) c union select * from d

还有一点就是UNION是过滤相同结果集求存不同结果集，而UNION ALL是全部累加一起。

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