Question

我有一个noobie问题：

我需要编写SQL脚本，从给定的一个列表@T返回3列结果集，整数字段为N，例如：

declare @t table(n int) 
insert into @t(n) values (3),(4),(5),
                         (6),(7),(8),
                         (9),(10),(11),
                         (13),(14),(15),
                         (16),(17),(18), (19)

结果3列表应该按行按升序包含表@T中的数据。如果表{2,4}中存在遗漏的值（例如，此处缺少@T 3），则结果集中的相应单元格应为NULL。

示例1：
对于值为{2,3,4,5}的表，结果表应如下所示：

NULL    2   3 
4    5  NULL

示例2：对于值为{2,4}的表，结果表应如下所示：

NULL    2   NULL 
4    NULL  NULL

Answer 1

你可以使用这样的数字表：

select T1.n, 
       T2.n, 
       T3.n 
from Numbers as N
  left outer join @T as T1
    on N.Number * 3 + 1 = T1.n
  left outer join @T as T2
    on N.Number * 3 + 2 = T2.n
  left outer join @T as T3
    on N.Number * 3 + 3 = T3.n
where N.Number between 0 and (select max(n) from @T) / 3

使用master..spt_values作为数字表格来处理示例。

declare @t table(n int) 
insert into @t(n) values (3),(4),(5),
                         (6),(7),(8),
                         (9),(10),(11),
                         (13),(14),(15),
                         (16),(17),(18), (19)


;with Numbers(Number) as
(
  select number
  from master..spt_values
  where type = 'P'
)

select T1.n, 
       T2.n, 
       T3.n 
from Numbers as N
  left outer join @T as T1
    on N.Number * 3 + 1 = T1.n
  left outer join @T as T2
    on N.Number * 3 + 2 = T2.n
  left outer join @T as T3
    on N.Number * 3 + 3 = T3.n
where N.Number between 0 and (select max(n) from @T) / 3

或者您可以使用带有数据透视表的数字表：

select [1], [2], [3]
from
  (
    select (N.Number - 1) / 3 as Number,
           T.n,
           1 + ((N.Number - 1) % 3) as rn
    from Numbers as N
      left outer join @T as T on
        N.Number = T.n
    where N.Number between 1 and (select max(n) from @T)
  ) as T
pivot
  (min(n) for rn in ([1], [2], [3])) as P

从列表中形成三列表

1 个答案: