在SQL Server中组合多行

我自己也弄不明白。希望有人能帮助我

我有三张桌子：用户、卡片、裁判和用户卡

用户：

裁判员：

卡片：

信用卡用户：

我想得到的结果是：

id   |   userName   |   refName   |   cards
1    |      u1      |    ref1     |   card1: red (123), card2: yellow (312)
2    |      u2      |    ref1     |   card2: yellow (523)
3    |      u3      |    ref2     |   card1: red (344)

等等

当用户有多张卡时，我只能得到多行。那么我怎样才能像这样组合它们呢

谢谢所有能帮助我的人！`

编辑：

目前我只使用左连接

---

我认为没有简单的方法可以格式化表的结果并将其附加到结果中。 您可以尝试使用以下内容执行存储过程：

CREATE TABLE #temp
(
    user_id int,
    CardString nvarchar(50)
)

CREATE TABLE #userCards
(
    user_id int,
    CardsList nvarchar(50)
)

DECLARE @UserID int,
        @cardName nvarchar(50),
        @cardList nvarchar(250) 

INSERT INTO #temp
SELECT user_id, cardName + ': ' + color + ' (' + number + ')'
FROM User_Cards AS UC
INNER JOIN Cards AS C ON C.card_id = UC.card_id

WHILE EXISTS (SELECT * FROM #temp)
BEGIN
   SELECT TOP(1) @UserID = user_id FROM #temp

   SET @cardList = ''

   WHILE EXISTS (SELECT * FROM #temp WHERE user_id = @UserID)
   BEGIN
      SELECT TOP(1) @cardName = [CardString] FROM #temp WHERE user_id = @UserID
      IF @cardList <> ''
         SET @cardList = @cardList + ', '
      SET @cardList = @cardList + @cardName
   END

   INSERT INTO #userCards
   VALUES (user_id, @cardList)
END

SELECT users.id, users.userName, referees.refName, CardsList 
FROM users
LEFT JOIN referees ON users.referee_id = referees.id
LEFT JOIN #userCards ON #userCards.card_id = users.user_id

DROP TABLE #userCards
DROP TABLE #temp

这将返回您想要的内容。

---

您还可以定义一个聚合函数，请参见

为什么要标记此问题以及？标题提到SQL Server…发布您当前使用的查询，以便我们更好地了解数据返回的方式。谢谢。这似乎很管用。但是，我怎么能同时返回空值呢？现在，如果用户没有任何卡片关联，那么cards列中的子查询将返回空值。如果希望允许空引用，还可以将内部连接更改为左连接。

id  |   cardName
--------------
1   |   card1
2   |   card2

user_id  |   card_id  |   color   |   number
-------------------------------------------
1        |   1        |   red     |   123
1        |   2        |   yellow  |   312
2        |   2        |   yellow  |   523
3        |   1        |   red     |   344

id   |   userName   |   refName   |   cards
1    |      u1      |    ref1     |   card1: red (123), card2: yellow (312)
2    |      u2      |    ref1     |   card2: yellow (523)
3    |      u3      |    ref2     |   card1: red (344)

SELECT UserName, refName cardName, color, number,
FROM users
LEFT JOIN referees ON users.referee_id = referees.id
LEFT JOIN users_cards ON users.id = users_cards.user_id
LEFT JOIN cards ON dbo.users_cards.card_id = cards.id

CREATE TABLE #temp
(
    user_id int,
    CardString nvarchar(50)
)

CREATE TABLE #userCards
(
    user_id int,
    CardsList nvarchar(50)
)

DECLARE @UserID int,
        @cardName nvarchar(50),
        @cardList nvarchar(250) 

INSERT INTO #temp
SELECT user_id, cardName + ': ' + color + ' (' + number + ')'
FROM User_Cards AS UC
INNER JOIN Cards AS C ON C.card_id = UC.card_id

WHILE EXISTS (SELECT * FROM #temp)
BEGIN
   SELECT TOP(1) @UserID = user_id FROM #temp

   SET @cardList = ''

   WHILE EXISTS (SELECT * FROM #temp WHERE user_id = @UserID)
   BEGIN
      SELECT TOP(1) @cardName = [CardString] FROM #temp WHERE user_id = @UserID
      IF @cardList <> ''
         SET @cardList = @cardList + ', '
      SET @cardList = @cardList + @cardName
   END

   INSERT INTO #userCards
   VALUES (user_id, @cardList)
END

SELECT users.id, users.userName, referees.refName, CardsList 
FROM users
LEFT JOIN referees ON users.referee_id = referees.id
LEFT JOIN #userCards ON #userCards.card_id = users.user_id

DROP TABLE #userCards
DROP TABLE #temp

SELECT users.id, UserName, refName,
 cards = (
    SELECT  
      STUFF(( 
           SELECT ', card' + CAST(ROW_NUMBER() OVER (ORDER BY cards.id) AS VARCHAR) 
                  +': '+ color + '(' + CAST(number AS VARCHAR) +')'
           FROM 
              users_cards
              LEFT JOIN cards ON dbo.users_cards.card_id = cards.id
           WHERE users.id = users_cards.user_id
           FOR XML PATH('')), 1, 1, '') 
  )
FROM users
LEFT JOIN referees ON users.refereeid = referees.id