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union order by 问题

时间：2011-12-21

来源：互联网

SQL code


---错误
select '' as a
union
select a from tb

order by cast(a as int) desc

---正确
select '' as a
union
select a from tb

order by a desc

为什么order by中加了函数就不行了呢？

作者: yubofighting 发布时间: 2011-12-21

SQL code

select '' as a,0 as aa
union
select a,cast(a as int) aa from tb

order by cast(a as int) desc

作者: kingtiy 发布时间: 2011-12-21

是不是因为第一条语句中a='',在cast('' as int )是出错？

作者: jwdream2008 发布时间: 2011-12-21

SQL code

如果该语句包含 UNION、INTERSECT 或 EXCEPT 运算符，则 ORDER BY 项必须出现在选择列表中。

作者: jwdream2008 发布时间: 2011-12-21

union 后 order by 是不是第一个cast为空了

作者: szstephenzhou 发布时间: 2011-12-21

SQL code

select '' as a,0 as aa
union
select a,cast(a as int) aa from tb
order by cast(a as int) desc

作者: fredrickhu 发布时间: 2011-12-21

引用 5 楼 fredrickhu 的回复:
SQL code

select '' as a,0 as aa
union
select a,cast(a as int) aa from tb
order by cast(a as int) desc

作者: qiujialongjjj 发布时间: 2011-12-21

引用 5 楼 fredrickhu 的回复:
SQL code

select '' as a,0 as aa
union
select a,cast(a as int) aa from tb
order by cast(a as int) desc

mark

作者: ju523756055 发布时间: 2011-12-21

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