大师作文网having count问题,sql达人来解决一下
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having count问题,sql达人来解决一下
having count(*)>5
这里的having count(*)>5是什么意思,最好用个例子说明
having count(*)>5
这里的having count(*)>5是什么意思,最好用个例子说明
having count(*)>5 指只显示分组後组内成员数大於5的资料
如有表A (col1,col2),值如下
col1 col2
A 1
A 10
A 5
A 6
A 7
A 2
B 4
B 9
select col1,sum(col2) as scol2 from A group by A having count(*) > 5;
则结果只会显示A的汇总,因为只是A的资料笔数大於五.
再问： select col1,sum(col2) as scol2 from A group by A having count(*) > 5; 最后的运行结果显示的是 col1 scol2 A 31 ?
再答： 应该是select col1,sum(col2) as scol2 from A group by col1 having count(*) > 5,不是group by A,这里写错了 结果是A 31
如有表A (col1,col2),值如下
col1 col2
A 1
A 10
A 5
A 6
A 7
A 2
B 4
B 9
select col1,sum(col2) as scol2 from A group by A having count(*) > 5;
则结果只会显示A的汇总,因为只是A的资料笔数大於五.
再问： select col1,sum(col2) as scol2 from A group by A having count(*) > 5; 最后的运行结果显示的是 col1 scol2 A 31 ?
再答： 应该是select col1,sum(col2) as scol2 from A group by col1 having count(*) > 5,不是group by A,这里写错了 结果是A 31
having count问题,sql达人来解决一下
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帮我解决一下数学问题,谢谢