Sql 如何将不同表中的多行合并为一行？

我正试图找回在我的数据库中注册的所有帐户，以及他们的“个人资料”图像和“封面”图像facebook风格的图像文件路径。映像文件路径存储在与其帐户表不同的表中

我的代码如下：

SELECT 
  a1.AccountID, 
 a1.Forename, 
  a1.Surname, 
  img1.Filename AS ProfileImg, 
  img2.Filename AS CoverImg
FROM
  dbo.Account a1
LEFT JOIN
  dbo.AccountImage img1 ON --table with images in
  img1.AccountID = a1.AccountID AND ProfileImg = 1 --boolean column to mark it as profile pic
LEFT JOIN
  dbo.AccountImage img2 ON --table with images in
  img2.AccountID = a1.AccountID and CoverImg = 1 --boolean column to flag as cover pic

科目表：

AccountID | Forename | Surname |
12345     | Ben      | Hur     |
12346     | Frodo    | Baggins |
12349     | Bill     | Gates   |

AccountImage表：

AccountID | Filename     | ProfileImg | CoverImg
12345     | face.jpg     | True       | NULL
12345     | bg.jpg       | NULL       | True
12346     | graph.png    | NULL       | NULL
12349     | sunset.jpg   | NULL       | True

当前返回：

|AccountID|Forename|Surname|ProfileImg|CoverImg  |
|    12345|     Ben|    Hur|NULL      |bg.jpg    |
|    12345|     Ben|    Hur|face.jpg  |NULL      |

我需要的结果

|AccountID|Forename|Surname|ProfileImg|CoverImg  |
|    12345|     Ben|    Hur|face.jpg  |bg.jpg    |

我只想为每个AccountID返回一行，其中分别包含它们的帐户详细信息和图像路径。有数百个帐户。否则我会得到重复的行——一行包含它们的ProfileImg文件路径，另一行包含它们的CoverImg文件路径

请注意，他们可能没有个人资料或封面图片。这意味着两列都可以为空。

试试这个

SELECT 
  a1.AccountID, 
 a1.Forename, 
  a1.Surname, 
  max(img1.Filename) AS ProfileImg, 
  max(img2.Filename) AS CoverImg
FROM
  dbo.Account a1
LEFT JOIN
  dbo.AccountImage img1 ON --table with images in
  img1.AccountID = a1.AccountID AND ProfileImg = 1 --boolean column to mark it as profile pic
LEFT JOIN
  dbo.AccountImage img2 ON --table with images in
  img2.AccountID = a1.AccountID and CoverImg = 2
GROUP BY 
 a1.AccountID, 
 a1.Forename, 
  a1.Surname

试试这个

SELECT 
  a1.AccountID, 
 a1.Forename, 
  a1.Surname, 
  max(img1.Filename) AS ProfileImg, 
  max(img2.Filename) AS CoverImg
FROM
  dbo.Account a1
LEFT JOIN
  dbo.AccountImage img1 ON --table with images in
  img1.AccountID = a1.AccountID AND ProfileImg = 1 --boolean column to mark it as profile pic
LEFT JOIN
  dbo.AccountImage img2 ON --table with images in
  img2.AccountID = a1.AccountID and CoverImg = 2
GROUP BY 
 a1.AccountID, 
 a1.Forename, 
  a1.Surname

---

只是你必须使用内部连接而不是左连接

SELECT 
  a1.AccountID, 
  a1.Forename, 
  a1.Surname, 
  img1.Filename AS ProfileImg, 
  img2.Filename AS CoverImg
FROM
  dbo.Account a1
INNER JOIN
  dbo.AccountImage img1 ON 
  img1.AccountID = a1.AccountID AND ProfileImg = 1 
INNER JOIN
  dbo.AccountImage img2 ON
  img2.AccountID = a1.AccountID and CoverImg = 2 

---

只是你必须使用内部连接而不是左连接

SELECT 
  a1.AccountID, 
  a1.Forename, 
  a1.Surname, 
  img1.Filename AS ProfileImg, 
  img2.Filename AS CoverImg
FROM
  dbo.Account a1
INNER JOIN
  dbo.AccountImage img1 ON 
  img1.AccountID = a1.AccountID AND ProfileImg = 1 
INNER JOIN
  dbo.AccountImage img2 ON
  img2.AccountID = a1.AccountID and CoverImg = 2 

---

这里有一个视图可以做到这一点。您需要确保在帐户映像表上设置了唯一的索引，以防止在特定帐户上设置每种类型的多个映像

SELECT AccountID, Forename, Surname,
(SELECT TOP (1) Filename
FROM dbo.AccountImage
WHERE (AccountID = dbo.Account.AccountID) AND (ProfileImg <> 0)) AS ProfileImg,
(SELECT TOP (1) Filename
 FROM dbo.AccountImage AS AccountImage_2
 WHERE (AccountID = dbo.Account.AccountID) AND (CoverImg <> 0)) AS CoverImg
FROM dbo.Account
WHERE ((SELECT COUNT(*) AS Expr1
FROM dbo.AccountImage AS AccountImage_1
WHERE (AccountID = dbo.Account.AccountID) AND (ProfileImg <> 0) OR
(AccountID = dbo.Account.AccountID) AND (CoverImg <> 0)) = 2)

---

这里有一个视图可以做到这一点。您需要确保在帐户映像表上设置了唯一的索引，以防止在特定帐户上设置每种类型的多个映像

SELECT AccountID, Forename, Surname,
(SELECT TOP (1) Filename
FROM dbo.AccountImage
WHERE (AccountID = dbo.Account.AccountID) AND (ProfileImg <> 0)) AS ProfileImg,
(SELECT TOP (1) Filename
 FROM dbo.AccountImage AS AccountImage_2
 WHERE (AccountID = dbo.Account.AccountID) AND (CoverImg <> 0)) AS CoverImg
FROM dbo.Account
WHERE ((SELECT COUNT(*) AS Expr1
FROM dbo.AccountImage AS AccountImage_1
WHERE (AccountID = dbo.Account.AccountID) AND (ProfileImg <> 0) OR
(AccountID = dbo.Account.AccountID) AND (CoverImg <> 0)) = 2)

---

你能使用MAXimg1.Filename、MAXimg2.Filename和GroupBy吗？我不知道它是否有效，但你尝试过GroupBy吗？我认为它应该有效，只要AccountID、ForName和姓氏相同。。。分组将起作用。请给出这3个表的一些示例数据。它不应该是您给我们的当前报税表，除非AccountImg获得了类似于ProfileImg=1的2行数据。其中1个文件名为null，另一个文件名为/filepath，我认为这不会造成任何影响sense@Raffaello.D.Huke我已经编辑了这个问题，将帐户和AccountImage表的示例数据包括在内。你能使用MAXimg1.Filename、MAXimg2.Filename和Group by吗？我不知道它是否有效，但你试过分组吗？我想应该可以，只要帐号、名字和姓氏相同。。。分组将起作用。请给出这3个表的一些示例数据。它不应该是您给我们的当前报税表，除非AccountImg获得了类似于ProfileImg=1的2行数据。其中1个文件名为null，另一个文件名为/filepath，我认为这不会造成任何影响sense@Raffaello.D.Huke我已经编辑了这个问题，将帐户和AccountImage表的示例数据包括在内，效果非常好，谢谢：。我更新的原始代码中有一个输入错误。它应该是CoverImg=1，因为它是一个布尔字段。工作非常好，谢谢：。我更新的原始代码中有一个输入错误。它应该是CoverImg=1，因为它是一个布尔字段。