标签:aa bb union days number smoke mysql id order
1、SQL1如下
SELECT aa.* FROM apas_smoke aa WHERE STATUS = 0 AND aa.area_id = 'd61523dda339441f80008634c6b91f60' AND aa.type = '3' AND to_days( create_time ) = to_days( now()) ORDER BY CAST( aa.smoke_number AS UNSIGNED ) ASC
查询结果如下,smoke_number 顺序为3,4
2、sql2如下:
SELECT bb.* FROM apas_smoke bb WHERE bb.STATUS = 0 AND bb.area_id = 'd61523dda339441f80008634c6b91f60' AND bb.type = '1' AND to_days( create_time ) = to_days( now()) ORDER BY CAST( bb.smoke_number AS UNSIGNED ) ASC
查询结果如下,smoke_number顺序为1,2
3、但是当使用UNION后,SQL如下
( SELECT aa.* FROM apas_smoke aa WHERE STATUS = 0 AND aa.area_id = 'd61523dda339441f80008634c6b91f60' AND aa.type = '3' AND to_days( create_time ) = to_days( now()) ORDER BY CAST( aa.smoke_number AS UNSIGNED ) ASC ) UNION ( SELECT bb.* FROM apas_smoke bb WHERE bb.STATUS = 0 AND bb.area_id = 'd61523dda339441f80008634c6b91f60' AND bb.type = '1' AND to_days( create_time ) = to_days( now()) ORDER BY CAST( bb.smoke_number AS UNSIGNED ) ASC )
查询结果,如下,smoke_number顺序与3,4,2,1 与预期的顺序 3,4,1,2不一致。
**原因:union(all)会使order by失效,解决办法,加limit
4、最终SQL
(
SELECT aa.* FROM apas_smoke aa WHERE STATUS = 0 AND aa.area_id = 'd61523dda339441f80008634c6b91f60' AND aa.type = '3' AND to_days( create_time ) = to_days( now()) ORDER BY CAST( aa.smoke_number AS UNSIGNED ) ASC LIMIT 2 )
UNION ( SELECT bb.* FROM apas_smoke bb WHERE bb.STATUS = 0 AND bb.area_id = 'd61523dda339441f80008634c6b91f60' AND bb.type = '1' AND to_days( create_time ) = to_days( now()) ORDER BY CAST( bb.smoke_number AS UNSIGNED ) ASC LIMIT 2 )
查询结果:
问题解决。
标签:aa,bb,union,days,number,smoke,mysql,id,order 来源: https://www.cnblogs.com/lansetuerqi/p/13986528.html
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