sql-server - 选择顶部进入不同的变量

Question

可能不可能，但我想我会问；

我想获取Top并将每个保存到不同的变量中。我知道可以进行 3 次选择并从中选择第 1、第 2、第 3，Top 3但我希望它可能在一个语句中？

IE

Declare @Var1 as int,
Declare @Var2 as int,
Declare @Var3 as int
select Top 3 [SAVE 3 RETURNED RECORDS INTO VARIABLES] from Table

Answer 1

假设出于演示目的，您想要TOP 3 schema_id FROM sys.objects ORDER BY object_id.

Declare @Var1 as int;
Declare @Var2 as int;
Declare @Var3 as int;


WITH T AS
(
SELECT *,
       ROW_NUMBER() OVER (ORDER BY object_id) RN
FROM sys.objects
)
SELECT @Var1 = MAX(CASE WHEN RN = 1 THEN schema_id END),
       @Var2 = MAX(CASE WHEN RN = 2 THEN schema_id END),
       @Var3 = MAX(CASE WHEN RN = 3 THEN schema_id END)
FROM T 
WHERE RN <= 3;

SELECT @Var1, @Var2, @Var3

它用于ROW_NUMBER对行进行编号，然后将它们转换为用于分配给变量的单行结果。

Answer 2

这是另一种方式：

Declare @Var1 as int, @Var2 as int, @Var3 as int
Declare @rn int = 1

select top(3) @Var1 = case when @rn = 1 then val else @var1 end,
              @Var2 = case when @rn = 2 then val else @var2 end,
              @Var3 = case when @rn = 3 then val else @var3 end,
              @rn += 1 
from t
order by val

select @var1, @var2, @var3