如何通过工会订购

Question

当数据来自多个选择并将它们组合在一起时,是否可以订购.例如

Select id,name,age
From Student
Where age < 15
Union
Select id,name,age
From Student
Where Name like "%a%"

如何按名称订购此查询.

有人说你可以查询这样的.

Select id,name,age
From Student
Where age < 15 or name like "%a%"
Order by name

但在这种情况下,我只是忽略了解决方案.

先感谢您.

Answer 1

写吧

Select id,name,age
From Student
Where age < 15
Union
Select id,name,age
From Student
Where Name like "%a%"
Order by name

order by应用于完整的结果集

Answer 2

Select id,name,age
from
(
   Select id,name,age
   From Student
   Where age < 15
  Union
   Select id,name,age
   From Student
   Where Name like "%a%"
) results
order by name

Answer 3

为了使排序仅适用于UNION中的第一个语句,您可以将其放在带UNION ALL的子选择中(这些似乎在Oracle中都是必需的):

Select id,name,age FROM 
(    
 Select id,name,age
 From Student
 Where age < 15
 Order by name
)
UNION ALL
Select id,name,age
From Student
Where Name like "%a%"

或者(解决Nicholas Carey的评论)你可以保证顶级SELECT是有序的,结果出现在底部SELECT之上,如下所示:

Select id,name,age, 1 as rowOrder
From Student
Where age < 15
UNION
Select id,name,age, 2 as rowOrder
From Student
Where Name like "%a%"
Order by rowOrder, name

Answer 4

其他答案都是正确的,但我认为值得注意的是,我遇到的地方没有意识到你需要别名的命令,并确保两个选择的别名是相同的......所以

select 'foo'
union
select item as `foo`
from myTable
order by `foo`

请注意,我在第一个选择中使用单引号,但在其他选项中使用反引号.

这将为您提供所需的分类.

Answer 5

Order By在之后应用union,所以只需order by在语句末尾添加一个子句:

Select id,name,age
From Student
Where age < 15
Union
Select id,name,age
From Student
Where Name like '%a%'
Order By name

Answer 6

如果我希望排序只应用于UNION中的一个,如果使用Union all:

Select id,name,age
From Student
Where age < 15
Union all
Select id,name,age
From 
(
Select id,name,age
From Student
Where Name like "%a%"
Order by name
)

Answer 7

如其他答案所述，LAST Union之后的“排序依据”应适用于通过union联接的两个数据集。

我当时有两个数据集，但是使用不同的表但使用相同的列。LAST Union之后的“订购依据”仍然无效。将ALIAS用于​​“ order by”中使用的列就可以了。

Select Name, Address for Employee 
Union
Select Customer_Name, Address from Customer
order by customer_name;   --Won't work

因此解决方案是使用别名“ User_Name”：

Select Name as User_Name, Address for Employee 
Union
Select Customer_Name as User_Name, Address from Customer
order by User_Name;