Question

我正在尝试创建一个SQL语句，将可变数量的行（最多5个）转换为单行。一小部分数据如下所示：

+--------------+--------+-------+-------+
|      ID      | ItemID | Style |  Qty  |
+--------------+--------+-------+-------+
| 00001-5A-2XL | F911-5 | F911  | 1.566 |
| 00001-5A-2XL | 233-5  | 233   | 0.236 |
| 00001-5A-3XL | F911-5 | F911  | 1.697 |
| 00001-5A-3XL | 233-5  | 233   | 0.237 |
| 00001-5A-4XL | F911-5 | F911  | 1.833 |
| 00001-5A-4XL | 233-5  | 233   | 0.239 |
| 00001-5A-L   | F911-5 | F911  | 1.307 |
| 00001-5A-L   | 233-5  | 233   | 0.234 |
+--------------+--------+-------+-------+

我希望将数据转换为如下所示：

+--------------+------+--------+-----+--------+----+--------+----+--------+----+--------+
|      ID      |  S1  | S1_Qty | S2  | S2_Qty | S3 | S3_Qty | S4 | S4_Qty | S5 | S5_Qty |
+--------------+------+--------+-----+--------+----+--------+----+--------+----+--------+
| 00001-5A-2XL | F911 | 1.566  | 233 | 0.236  |    |        |    |        |    |        |
| 00001-5A-3XL | F911 | 1.566  | 233 | 0.237  |    |        |    |        |    |        |
| 00001-5A-4XL | F911 | 1.566  | 233 | 0.239  |    |        |    |        |    |        |
| 00001-5A-L   | F911 | 1.566  | 233 | 0.234  |    |        |    |        |    |        |
+--------------+------+--------+-----+--------+----+--------+----+--------+----+--------+

在轮播时我有点迷失，特别是当我想将Style和Quantity同时转移到我的列中时。我最多需要将5个样式（行）转换为最多5列。

任何建议，指示等都将不胜感激。

Answer 1

根据您的需要，您可以通过几种不同的方式获得结果。

目前还不是很清楚你是否需要使用两种不同的聚合来获得结果。如果你需要sum(qty)，然后在max()上使用style，我建议使用带有CASE表达式的聚合函数来获得结果：

select id,
  max(case when ItemID = 'F911-5' then Style end) Style1,
  sum(case when ItemID = 'F911-5' then Qty else 0 end) Qty1,
  max(case when ItemID = '233-5' then Style end) Style2,
  sum(case when ItemID = '233-5' then Qty else 0 end) Qty2
from yourtable
group by id;

见SQL Fiddle with Demo。然后，当您有新的ItemId值时，您只需添加新列。

您也可以使用PIVOT功能，但由于您需要在两列上进行PIVOT，我首先要忽略style和Qty列。这会将您的多列数据转换为多行，您可以使用UNPIVOT函数或CROSS APPLY获得结果 - 基本语法为：

select id, 
  col = col+cast(seq as varchar(10)), value
from
(
  select id, itemid, style, qty,
    row_number() over(partition by id
                      order by qty desc) seq
  from yourtable
) src
cross apply
(
  select 'style', style union all
  select 'qty', cast(qty as varchar(10))
) c(col, value)

见SQL Fiddle with Demo。这会将您的数据转换为多行，然后可以进行旋转：

|           ID |    COL |   VALUE |
|--------------|--------|---------|
| 00001-5A-2XL | style1 |    F911 |
| 00001-5A-2XL |   qty1 | 1.56600 |
| 00001-5A-2XL | style2 |     233 |
| 00001-5A-2XL |   qty2 | 0.23600 |
| 00001-5A-3XL | style1 |    F911 |

然后您可以应用PIVOT函数来获得最终结果：

select id, style1, qty1, style2, qty2
from
(
  select id, 
    col = col+cast(seq as varchar(10)), value
  from
  (
    select id, itemid, style, qty,
      row_number() over(partition by id
                        order by qty desc) seq
    from yourtable
  ) src
  cross apply
  (
    select 'style', style union all
    select 'qty', cast(qty as varchar(10))
  ) c(col, value)
) d
pivot
(
  max(value)
  for col in (style1, qty1, style2, qty2)
) piv;

见SQL Fiddle with Demo。最后，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：

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 id
                                                order by qty desc) seq
                      from yourtable
                    ) t
                    cross apply
                    (
                      select 'style', 1 union all
                      select 'qty', 2
                    ) c (col, so)
                    group by col, so, seq
                    order by seq, so
            FOR XML PATH(''), TYPE
            ).value('.', 'NVARCHAR(MAX)') 
        ,1,1,'')

set @query = 'SELECT id, ' + @cols + ' 
             from 
             (
                select id, 
                  col = col+cast(seq as varchar(10)), value
                from
                (
                  select id, itemid, style, qty,
                    row_number() over(partition by id
                                      order by qty desc) seq
                  from yourtable
                ) src
                cross apply
                (
                  select ''style'', style union all
                  select ''qty'', cast(qty as varchar(10))
                ) c(col, value)
            ) x
            pivot 
            (
                max(value)
                for col in (' + @cols + ')
            ) p '

execute sp_executesql @query;

见SQL Fiddle with Demo。结果如下：

|           ID | STYLE1 |    QTY1 | STYLE2 |    QTY2 |
|--------------|--------|---------|--------|---------|
| 00001-5A-2XL |   F911 | 1.56600 |    233 | 0.23600 |
| 00001-5A-3XL |   F911 | 1.69700 |    233 | 0.23700 |
| 00001-5A-4XL |   F911 | 1.83300 |    233 | 0.23900 |
|   00001-5A-L |   F911 | 1.30700 |    233 | 0.23400 |

如何在多列上进行透视

1 个答案: