从列表中形成三列表

Question

我有一个noobie问题:

我需要编写SQL脚本,该脚本从给定的一个@T具有整数字段N的列表中返回3列结果集,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@T按行按升序包含表中的数据.如果表中存在遗漏值(例如,{2,4}此处缺少3个)@T,则结果集中的相应单元格应为NULL.

示例1:
对于具有值{2,3,4,5} 的表,结果表应如下所示:

NULL    2   3 
4    5  NULL 

示例2:对于具有值{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作为数字表的工作样本.

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