SQL将行转置为列(按键变量分组)？

Question

我试图将行转换为列,按唯一标识符(CASE_ID)进行分组.

我有一个这种结构的表:

CASE_ID..AMOUNT..TYPE
100 ........ 10 ....... A
100 ........ 50 ....... B
100 ...... ..75 ....... A
200 ........ 33 ....... B
200 ........ 10 ....... C.

而我正试图查询它以产生这种结构......

CASE_ID ... AMOUNT_1 ... TYPE_1 ... AMOUNT_2 ... TYPE_2 ... AMOUNT_3 ... TYPE_3
100 ........... 10 ............ ......一个............. 50 ..................乙.......... ... 75 ................... A
200 ........... 33 ............. .....乙............. 10 ..................ç........... (空)...............(空)

(假设有更大的数据集,包含CASE_ID,TYPE和AMOUNT的大量可能值)

我尝试使用数据透视表,但我不需要聚合函数(只是尝试重组数据).现在我试图以某种方式使用row_number但不确定如何.

我基本上试图复制和SPSS命令调用Casestovars,但需要能够在SQL中执行它.谢谢.

Answer 1

您可以通过创建序列号来获得结果row_number(),然后使用带有CASE表达式的聚合函数:

select case_id,
  max(case when seq = 1 then amount end) amount1,
  max(case when seq = 1 then type end) type1,
  max(case when seq = 2 then amount end) amount2,
  max(case when seq = 2 then type end) type2,
  max(case when seq = 3 then amount end) amount3,
  max(case when seq = 3 then type end) type3
from 
(
  select case_id, amount, type,
    row_number() over(partition by case_id
                      order by case_id) seq
  from yourtable
) d
group by case_id;

请参阅SQL Fiddle with Demo.

如果您正在使用具有PIVOT功能的数据库产品,那么您可以使用row_number()PIVOT,但首先我建议您首先取消对列amount和type列的拆分.SQL Server中有限数量的值的基本语法是:

select case_id, amount1, type1, amount2, type2, amount3, type3
from
(
  select case_id, col+cast(seq as varchar(10)) as col, value
  from 
  (
    select case_id, amount, type,
      row_number() over(partition by case_id
                        order by case_id) seq
    from yourtable
  ) d
  cross apply
  (
    select 'amount', cast(amount as varchar(20)) union all
    select 'type', type
  ) c (col, value)
) src
pivot
(
  max(value)
  for col in (amount1, type1, amount2, type2, amount3, type3)
) piv;

请参阅SQL Fiddle with Demo.

如果您有一个未知数量的值,那么您可以使用动态SQL来获得结果 - SQL Server语法将是:

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

select @cols = STUFF((SELECT ',' + QUOTENAME(col+cast(seq as varchar(10))) 
                    from
                    (
                      select row_number() over(partition by case_id
                                                order by case_id) seq
                      from yourtable
                    ) d
                    cross apply
                    (
                      select 'amount', 1 union all
                      select 'type', 2
                    ) c (col, so)
                    group by col, so
                    order by seq, so
            FOR XML PATH(''), TYPE
            ).value('.', 'NVARCHAR(MAX)') 
        ,1,1,'')

set @query = 'SELECT case_id,' + @cols + ' 
             from 
             (
                select case_id, col+cast(seq as varchar(10)) as col, value
                from 
                (
                  select case_id, amount, type,
                    row_number() over(partition by case_id
                                      order by case_id) seq
                  from yourtable
                ) d
                cross apply
                (
                  select ''amount'', cast(amount as varchar(20)) union all
                  select ''type'', type
                ) c (col, value)
            ) x
            pivot 
            (
                max(value)
                for col in (' + @cols + ')
            ) p '

execute sp_executesql @query;

请参阅SQL Fiddle with Demo.每个版本都会给出结果:

| CASE_ID | AMOUNT1 | TYPE1 | AMOUNT2 | TYPE2 | AMOUNT3 |  TYPE3 |
|---------|---------|-------|---------|-------|---------|--------|
|     100 |      10 |     A |      50 |     B |      75 |      A |
|     200 |      33 |     B |      10 |     C |  (null) | (null) |