Mysql竟然不支持同一个表的关联查询

本文探讨了MySQL在自关联查询方面的限制,即无法在同一SQL语句中多次引用同一张表,并给出了通过创建临时表来规避这一限制的方法。

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晕!Mysql竟然不支持将同一个表用不同的别名进行关联查询,甚至不能在一条sql语句中两次使用同一个表。
错误提示: #1137 - Can't reopen table: 'mytable'
createTEMPORARYtabletemp1as
select*from(
select1asid,50asic,'2007-10-8'asitime,'a'aswdunion
select2asid,80asic,'2007-10-9'asitime,'ab'aswdunion
select3asid,50asic,'2007-11-3'asitime,'abc'aswdunion
select4asid,50asic,'2007-6-8'asitime,'ad'aswdunion
select5asid,60asic,'2007-4-9'asitime,'ac'aswdunion
select6asid,80asic,'2007-12-9'asitime,'aa'aswd
)a;

createTEMPORARYtabletemp2as
select*from(
select1asid,50asic,'2007-10-8'asitime,'a'aswdunion
select2asid,80asic,'2007-10-9'asitime,'ab'aswdunion
select3asid,50asic,'2007-11-3'asitime,'abc'aswdunion
select4asid,50asic,'2007-6-8'asitime,'ad'aswdunion
select5asid,60asic,'2007-4-9'asitime,'ac'aswdunion
select6asid,80asic,'2007-12-9'asitime,'aa'aswd
)a;

selectmin(a.id)asid,a.ic,a.itime,a.wd
fromtemp1ainnerjoin
(
selectic,max(cast(itimeasdate))asitimefromtemp2groupbyic
)b
ona.ic=b.icandcast(a.itimeasdate)=cast(b.itimeasdate)
groupbya.id,a.ic,a.itime,a.wd
orderbya.wd

(当然也可以用其他方式变通解决)或者:
createTEMPORARYtablemytableas
select*from(
select1asid,50asic,'2007-10-8'asitime,'a'aswdunion
select2asid,80asic,'2007-10-9'asitime,'ab'aswdunion
select3asid,50asic,'2007-11-3'asitime,'abc'aswdunion
select4asid,50asic,'2007-6-8'asitime,'ad'aswdunion
select5asid,60asic,'2007-4-9'asitime,'ac'aswdunion
select6asid,80asic,'2007-12-9'asitime,'aa'aswd
)a;

createTEMPORARYtabletempas
select*from(
selectic,max(cast(itimeasdate))asitimefrommytablegroupbyic
)a;

selectmin(a.id)asid,a.ic,a.itime,a.wd
frommytableainnerjointempbona.ic=b.icandcast(a.itimeasdate)=cast(b.itimeasdate)
groupbya.id,a.ic,a.itime,a.wd
orderbya.wd
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