从SQL中的复杂选择中连接行

Question

RDBMS是SQL Server 2008。

我有3张桌子。为了简化，它们看起来像这样：

NominationOrder表：

NominationOrderId | NominationId
         1        |      5
         2        |      9

NominationOrderItem表：

NominationOrderItemId | NominationOrderId | GiftId
           1          |         1         |    6
           2          |         1         |    3
           3          |         1         |    9

Gift表：

GiftId | GiftName |
  3    |   TVSet
  6    |  TabletPC
  9    | LittlePonny

所以，有一些Nomination。每个Nomination可能有1个Nomination Order。每个Nomination Order可能包含多个Nomination Order Items，每个Gift都会引用此订单中的某些Gift。

我正在为Reporting Services报告，我需要在一行中显示每个Gift提名的数据，并显示连接的NominationId | NominationOrderId | GiftName 5 | 1 | TVSet 5 | 1 | TabletPC 5 | 1 | LittlePonny 个名称。

目前它看起来像这样：

NominationId | NominationOrderId |           GiftName
      5      |          1        |   TVSet, TabletPC, LittlePonny

我需要它看起来像这样：

  select 
    nn.NominationId
    ,n_o.NominationOrderId
    ,g.name GiftName
from dbo.Nomination nn
    LEFT JOIN dbo.NominationOrder n_o ON n_o.NominationId = nn.NominationId
    LEFT JOIN dbo.NominationOrderItem noi ON noi.NominationOrderId = n_o.NominationOrderId
    left join dbo.Gift g on g.GiftId = noi.GiftId

当前SQL查询的简化示例：

{{1}}

如何重写它以在单个字符串中输出并连接礼品名称？

Answer 1

SELECT result.NominationId, Substring(result.Gifts,3,Len(result.Gifts) - 3)
FROM (
    SELECT 
    NominationId, 
    (SELECT ', ' + CAST(g.GiftName AS varchar(MAX)) 
        FROM NominationOrder i 
        INNER JOIN NominationOrderItem noi on i.NominationOrderId = noi.NominationOrderId
        INNER JOIN Gift g on noi.GiftId = g.GiftId
        WHERE i.NominationId = n.NominationId
        FOR XML PATH (''))
         AS Gifts
    FROM NominationOrder n
    GROUP BY NominationId
) result

Answer 2

您可以使用CTE：

WITH cteTbl (NominationId, NominationOrderId, GiftName) AS ( Your Query here)

然后使用NominationId将所有行与NominationOrderId和FOR XML PATH('')连接在一起，之后用,替换第一个逗号STUFF：

SELECT t.NominationId
     , t.NominationOrderId
     , STUFF( ( SELECT ', ' + GiftName
                FROM cteTbl
                WHERE NominationId = t.NominationId
                  AND NominationOrderId = t.NominationOrderId
                ORDER BY GiftName DESC
                FOR XML PATH('') ), 1, 1, '')
FROM cteTbl t 
GROUP BY t.NominationId
       , t.NominationOrderId

SQLFiddle