sql - 动态创建列sql

Question

我有一张客户表

Customer ID        Name         
   1               John        
   2               Lewis        
   3               Mary         

我有另一张桌子 CustomerRewards

 TypeID           Description
   1                Bronze
   2                Silver
   3                Gold
   4               Platinum
   5               AnotherOne

还有决赛桌

 RewardID          TypeID          CustomerID
    1                1                 1
    2                1                 1
    3                2                 1
    4                2                 2

customerTypes 表是动态的，其中许多类型可以添加和删除。基本上我想要的只是动态生成的列和每个列的计数，比如

CustomerName        Bronze        Silver     Gold      Platinum     AnotherOne    total
   John               2             1         0           0             0           3
   Lewis              0             1         0           0             0           1
 Grand TOTAL          2             2         0           0             0           4

像我说的问题是类型是动态的，客户是动态的，所以我需要根据系统中的类型动态列

我已经在 DataGridView 中标记了 c#，因为我需要它

提前致谢

Answer 1

您将需要为此使用PIVOT函数。如果您有已知数量的列，则可以对这些值进行硬编码：

select name, [Bronze], [Silver], [Gold], [Platinum], [AnotherOne]
from
(
  select c.name,
    cr.description,
    r.typeid
  from customers c
  left join rewards r
    on c.id = r.customerid
  left join customerrewards cr
    on r.typeid = cr.typeid
) x
pivot
(
  count(typeid)
  for description in ([Bronze], [Silver], [Gold], [Platinum], [AnotherOne])
) p;

请参阅SQL Fiddle with Demo。

现在，如果您有未知数量的列，那么您可以使用动态 SQL 来PIVOT：

DECLARE @cols AS NVARCHAR(MAX),
    @query  AS NVARCHAR(MAX)

select @cols = STUFF((SELECT ',' + QUOTENAME(description) 
                    from customerrewards
                    group by description, typeid
                    order by typeid
            FOR XML PATH(''), TYPE
            ).value('.', 'NVARCHAR(MAX)') 
        ,1,1,'')

set @query = 'SELECT name,' + @cols + ' from 
             (
                select c.name,
                  cr.description,
                  r.typeid
                from customers c
                left join rewards r
                  on c.id = r.customerid
                left join customerrewards cr
                  on r.typeid = cr.typeid
            ) x
            pivot 
            (
                count(typeid)
                for description in (' + @cols + ')
            ) p '

execute(@query)

请参阅带有演示的 SQL Fiddle

如果需要包含该Total列，则可以使用ROLLUP（静态版本演示）：

select name, sum([Bronze]) Bronze, sum([Silver]) Silver, 
  sum([Gold]) Gold, sum([Platinum]) Platinum, sum([AnotherOne]) AnotherOne
from 
(
  select name, [Bronze], [Silver], [Gold], [Platinum], [AnotherOne]
  from
  (
    select c.name,
      cr.description,
      r.typeid
    from customers c
    left join rewards r
      on c.id = r.customerid
    left join customerrewards cr
      on r.typeid = cr.typeid
  ) x
  pivot
  (
    count(typeid)
    for description in ([Bronze], [Silver], [Gold], [Platinum], [AnotherOne])
  ) p
) x
group by name with rollup

动态版（Demo）：

DECLARE @cols AS NVARCHAR(MAX),
    @colsRollup AS NVARCHAR(MAX),
    @query  AS NVARCHAR(MAX)

select @cols = STUFF((SELECT ',' + QUOTENAME(description) 
                    from customerrewards
                    group by description, typeid
                    order by typeid
            FOR XML PATH(''), TYPE
            ).value('.', 'NVARCHAR(MAX)') 
        ,1,1,'')

select @colsRollup 
      = STUFF((SELECT ', Sum(' + QUOTENAME(description) + ') as '+ QUOTENAME(description)
                    from customerrewards
                    group by description, typeid
                    order by typeid
            FOR XML PATH(''), TYPE
            ).value('.', 'NVARCHAR(MAX)') 
        ,1,1,'')


set @query 
          = 'SELECT name, '+ @colsRollup + '
             FROM
             (
                SELECT name,' + @cols + ' from 
                 (
                    select c.name,
                      cr.description,
                      r.typeid
                    from customers c
                    left join rewards r
                      on c.id = r.customerid
                    left join customerrewards cr
                      on r.typeid = cr.typeid
                ) x
                pivot 
                (
                    count(typeid)
                    for description in (' + @cols + ')
                ) p 
              ) x1
              GROUP BY name with ROLLUP'

execute(@query)