将联合查询的结果排序

[kel]

从几个表中联合查询，然后将结果按一字段排序。如：
select a1,a2,a3 from a union select b1,b2,b3 from b union select c1,c2,c3
from c
其中，a1,b1,c1为日期字段。如何才能做到将查出来的结果按日期排序。

[snowy_howe]

order by 1

[kel]

什么意思,能不能详细点?

[snowy_howe]

select a1,a2,a3 from a
union
select b1,b2,b3 from b
union
select c1,c2,c3 from c
order by 1 [asc/desc]
asc为升序，desc为降序

[kel]

我知道了.ORDER BY 1也就是按第一个字段排.
不嫌麻烦,也可将其作为子查询来处理.将日期字段另取一个相同的别名就可以了.

[wsfx]

你可以为每个字查询中要排序的列起一个相同的名字：
select a1 as myDate,a2,a3 from a
union
select b1 as myDate,b2,b3 from b
union
select c1 as myDate,c2,c3 from c
order by myDate asc