SQL：从视图中聚合函数选取的行中获取列
SQL: Taking Column From a Row Picked By Aggregate Function in View
我有三个 SQL tables：Release（表示电影的发行），Media（表示那些版本；即对于 Blu-ray/DVD 组合，Media 中将有两行，一张蓝光和一张 DVD，指向 Release) 和 [=21 中的同一行=]（定义蓝光、DVD、VHS 等）。 Release/Media 和 MediaType/Media 是一对多的关系，Media 在两者的 "many" 一侧关系。我有一个 Release、vRelease 的视图，其中包含聚合函数，例如显示与该版本关联的媒体数量的 COUNT。到目前为止，这是我对该视图的看法：
SELECT dbo.Release.ReleaseID
,dbo.Release.Name
,CASE WHEN Release.Compilation = 0 THEN 'No' WHEN Release.Compilation = 1 THEN 'Yes' END AS Compilation
,dbo.Release.Owner
,CASE WHEN Release.LentOut = 0 THEN 'No' WHEN Release.LentOut = 1 THEN 'Yes' END AS LentOut
,COUNT(dbo.Media.ReleaseID) AS NumberOfMedia
,MIN(dbo.Media.MediaID) AS FirstMediaID
,MIN(dbo.MediaType.Name) AS FirstMediaType
FROM dbo.MediaType INNER JOIN
dbo.Media ON dbo.MediaType.MediaTypeID = dbo.Media.MediaTypeID RIGHT OUTER JOIN
dbo.Release ON dbo.Media.ReleaseID = dbo.Release.ReleaseID
GROUP BY dbo.Release.ReleaseID, dbo.Release.Name, dbo.Release.Compilation, dbo.Release.Owner, dbo.Release.LentOut
您会注意到我还包含了另外两个聚合列：FirstMediaID 获取与 Media table 中最先出现的版本关联的媒体 ID （即，如果一个发行版有两张与之相关联的 DVD，它会获得一张 ID 值较低的 DVD）。这个专栏本身没有用；然后，我想做的是依次获取与 Media 相关联的 MediaType。换句话说，我想要一个显示第一个 Media 的 MediaType 的列，它附加到每个 Release。之后的列 FirstMediaType 应该这样做，但它却在与 Release 关联的所有 Media 中获取 MediaType 并选择一个按字母顺序排列 - 这意味着 Blu-ray 将始终优先于 DVD（这很好），但音频 CD 将始终优先于其他所有内容（这不好）。
如何获取此视图中的 FirstMediaType 列以获取 FirstMediaID 中标识的媒体的 MediaType？
更新：这里是 tables，它们的列和一些示例行。
来自Release的一对：
+-----------+----------------------------------------+-------+-------------+---------+
| ReleaseID | Name | Owner | Compilation | LentOut |
+-----------+----------------------------------------+-------+-------------+---------+
| 2 | Alice in Wonderland | NULL | 0 | 0 |
| 6 | 4 Film Favorites - Family Comedies | NULL | 1 | 0 |
| 8 | Aladdin | NULL | 0 | 0 |
| 463 | Harry Potter and the Half-Blood Prince | NULL | 0 | 1 |
| 534 | Spirited Away | Ryan | 0 | 0 |
| 571 | The Original Christmas Classics | NULL | 1 | 0 |
+-----------+----------------------------------------+-------+-------------+---------+
Compilation 表示发行版中包含不止一部电影。
Media中对应条目：
+---------+-------------+-------------------------------------------------------------------------------------+-----------+
| MediaID | MediaTypeID | Name | ReleaseID |
+---------+-------------+-------------------------------------------------------------------------------------+-----------+
| 2 | 2 | Movie | 2 |
| 3 | 1 | Movie | 2 |
| 12 | 1 | Space Jam; Looney Tunes: Back in Action | 6 |
| 13 | 1 | Funky Monkey; Osmosis Jones | 6 |
| 17 | 3 | Movie | 8 |
| 620 | 1 | Movie | 463 |
| 726 | 1 | Movie | 534 |
| 807 | 1 | Rudolph the Red-Nosed Reindeer; Cricket on the Hearth | 571 |
| 808 | 1 | Frosty the Snowman; Frosty Returns | 571 |
| 809 | 1 | Santa Claus is Comin' to Town!; Mr. Magoo's Christmas Carol; The Little Drummer Boy | 571 |
| 810 | 4 | Tracks 1-7 | 571 |
+---------+-------------+-------------------------------------------------------------------------------------+-----------+
MediaType中的前几名：
+-------------+--------------+
| MediaTypeID | Name |
+-------------+--------------+
| 1 | DVD Disc |
| 2 | Blu-ray Disc |
| 3 | VHS |
| 4 | Audio CD |
+-------------+--------------+
vRelease中对应的条目应该是这样的：
+-----------+----------------------------------------+-------------+-------+---------+---------------+--------------+----------------+
| ReleaseID | Name | Compilation | Owner | LentOut | NumberOfMedia | FirstMediaID | FirstMediaType |
+-----------+----------------------------------------+-------------+-------+---------+---------------+--------------+----------------+
| 2 | Alice in Wonderland | No | NULL | No | 2 | 2 | Blu-ray Disc |
| 6 | 4 Film Favorites - Family Comedies | Yes | NULL | No | 2 | 12 | DVD Disc |
| 8 | Aladdin | No | NULL | No | 1 | 17 | VHS |
| 463 | Harry Potter and the Half-Blood Prince | No | NULL | Yes | 1 | 620 | DVD Disc |
| 534 | Spirited Away | No | Ryan | No | 1 | 726 | DVD Disc |
| 571 | The Original Christmas Classics | Yes | NULL | No | 4 | 807 | DVD Disc |
+-----------+----------------------------------------+-------------+-------+---------+---------------+--------------+----------------+
但实际上是这样的：
+-----------+----------------------------------------+-------------+-------+---------+---------------+--------------+----------------+
| ReleaseID | Name | Compilation | Owner | LentOut | NumberOfMedia | FirstMediaID | FirstMediaType |
+-----------+----------------------------------------+-------------+-------+---------+---------------+--------------+----------------+
| 2 | Alice in Wonderland | No | NULL | No | 2 | 2 | Blu-ray Disc |
| 6 | 4 Film Favorites - Family Comedies | Yes | NULL | No | 2 | 12 | DVD Disc |
| 8 | Aladdin | No | NULL | No | 1 | 17 | VHS |
| 463 | Harry Potter and the Half-Blood Prince | No | NULL | Yes | 1 | 620 | DVD Disc |
| 534 | Spirited Away | No | Ryan | No | 1 | 726 | DVD Disc |
| 571 | The Original Christmas Classics | Yes | NULL | No | 4 | 807 | Audio CD |
+-----------+----------------------------------------+-------------+-------+---------+---------------+--------------+----------------+
问题出在最后一个。
最简单的方法是在 FirstMediaId = MediaType.MediaId
上向您的 MediaType table 添加另一个连接
;WITH data AS (
SELECT dbo.Release.ReleaseID
,dbo.Release.Name
,CASE WHEN Release.Compilation = 0 THEN 'No' WHEN Release.Compilation = 1 THEN 'Yes' END AS Compilation
,dbo.Release.Owner
,CASE WHEN Release.LentOut = 0 THEN 'No' WHEN Release.LentOut = 1 THEN 'Yes' END AS LentOut
,COUNT(dbo.Media.ReleaseID) AS NumberOfMedia
,MIN(dbo.Media.MediaID) AS FirstMediaID
FROM dbo.MediaType
INNER JOIN dbo.Media
ON dbo.MediaType.MediaTypeID = dbo.Media.MediaTypeID
RIGHT OUTER JOIN dbo.Release
ON dbo.Media.ReleaseID = dbo.Release.ReleaseID
GROUP BY dbo.Release.ReleaseID, dbo.Release.Name, dbo.Release.Compilation, dbo.Release.Owner, dbo.Release.LentOut
)
SELECT data.ReleaseId
,data.Name
,data.Compilation
,data.Owner
,data.LentOut
,data.NumberOfMedia
,data.FirstMediaId
,MediaType.Name as FirstMediaName
FROM data
LEFT OUTER JOIN dbo.MediaType
ON data.FirstMediaId = MediaType.MediaTypeId
returns整行与"First"、"Last"、"Earliest"、"Latest"等需求相关联的一个非常方便的技术是使用row_number() over()。这里你想要"first media type"，所以它在这里是相关的。
正如您将在以下查询中看到的那样，加入 [Media] table 被替换为包含行号计算的子查询。这里我们partition byReleaseID和order byMediaID，所以，对于each ReleaseID 第一行将是具有最低 MediaID 值的行。然后在这个派生的 table 的连接中添加一个额外的条件以仅考虑行号为 1.
的行
建议查询
SELECT
r.ReleaseID
, m.MediaID
, mt.MediaTypeID
, mt.name MediaName
, r.Name
, CASE
WHEN r.Compilation = 0 THEN 'No'
WHEN r.Compilation = 1 THEN 'Yes'
END AS compilation
, r.Owner
, CASE
WHEN r.LentOut = 0 THEN 'No'
WHEN r.LentOut = 1 THEN 'Yes'
END AS lentout
FROM dbo.Release r
INNER JOIN (
SELECT
Media.*
, ROW_NUMBER() OVER(PARTITION BY ReleaseID
ORDER BY MediaID) AS rn
FROM dbo.Media
) m ON r.ReleaseID = m.ReleaseID and rn = 1
INNER JOIN dbo.MediaType mt ON m.MediaTypeID = mt.MediaTypeID
结果
| ReleaseID | MediaID | MediaTypeID | MediaName | Name | compilation | Owner | lentout |
|-----------|---------|-------------|--------------|----------------------------------------|-------------|--------|---------|
| 2 | 2 | 2 | Blu-ray Disc | Alice in Wonderland | No | (null) | No |
| 6 | 12 | 1 | DVD Disc | 4 Film Favorites - Family Comedies | Yes | (null) | No |
| 8 | 17 | 3 | VHS | Aladdin | No | (null) | No |
| 463 | 620 | 1 | DVD Disc | Harry Potter and the Half-Blood Prince | No | (null) | Yes |
| 534 | 726 | 1 | DVD Disc | Spirited Away | No | Ryan | No |
| 571 | 807 | 1 | DVD Disc | The Original Christmas Classics | Yes | (null) | No |
我最终找到了一种简单的方法来做我想做的事。它不像 Used_By_Already 的答案那么花哨（据我所知，它确实有效）并且可能在某处打破了 SQL 最佳实践规则，但它更容易理解和保持——至少对我的新手来说是这样。
由于问题是试图让视图使用它在连接中计算的聚合列，我只是将两步操作拆分为两个视图。 vReleasePre 包含我在原始查询中概述的所有列，FirstMediaType 除外。 vRelease 现在只需从 vReleasePre 中获取所有列并添加 FirstMediaType，它从末尾的连接中获取其值：LEFT OUTER JOIN dbo.vMedia ON dbo.vReleasePre.FirstMediaID = dbo.vMedia.MediaID，其中 vMedia 是包含 Media 中所有列的视图，加上 MediaType 列（我已经有 vMedia 了）。
由于此数据库通过 Entity Framework 在 ASP.NET MVC 网络应用程序中使用，并且 EF 对数据模型将接受和不接受的内容一直很奇怪，我想一个简单但迂回的解决方案可能是我的最佳选择。
vReleasePre:
SELECT dbo.Release.ReleaseID
,dbo.Release.Name
,CASE WHEN Release.Compilation = 0 THEN 'No' WHEN Release.Compilation = 1 THEN 'Yes' END AS Compilation
,dbo.Release.Owner
,CASE WHEN Release.LentOut = 0 THEN 'No' WHEN Release.LentOut = 1 THEN 'Yes' END AS LentOut
,COUNT(dbo.Media.ReleaseID) AS NumberOfMedia
,MIN(dbo.Media.MediaID) AS FirstMediaID
FROM dbo.MediaType INNER JOIN
dbo.Media ON dbo.MediaType.MediaTypeID = dbo.Media.MediaTypeID RIGHT OUTER JOIN
dbo.Release ON dbo.Media.ReleaseID = dbo.Release.ReleaseID
GROUP BY dbo.Release.ReleaseID, dbo.Release.Name, dbo.Release.Compilation, dbo.Release.Owner, dbo.Release.LentOut
vRelease:
SELECT dbo.vReleasePre.ReleaseID
,dbo.vReleasePre.Name
,dbo.vReleasePre.Compilation
,dbo.vReleasePre.Owner
,dbo.vReleasePre.LentOut
,dbo.vReleasePre.NumberOfMedia
,dbo.vMedia.MediaType
FROM dbo.vReleasePre LEFT OUTER JOIN
dbo.vMedia ON dbo.vReleasePre.FirstMediaID = dbo.vMedia.MediaID
对于新手来说，这是我使用的子查询
SELECT
ROW_NUMBER() OVER(PARTITION BY ReleaseID
ORDER BY MediaID) AS rn
, Media.*
FROM dbo.Media
这就是它的作用（参见 rn 列）
| rn | MediaID | MediaTypeID | Name | ReleaseID |
|----|---------|-------------|-------------------------------------------------------------------------------------|-----------|
| 1 | 2 | 2 | Movie | 2 |
| 2 | 3 | 1 | Movie | 2 |
| 1 | 12 | 1 | Space Jam; Looney Tunes: Back in Action | 6 |
| 2 | 13 | 1 | Funky Monkey; Osmosis Jones | 6 |
| 1 | 17 | 3 | Movie | 8 |
| 1 | 620 | 1 | Movie | 463 |
| 1 | 726 | 1 | Movie | 534 |
| 1 | 807 | 1 | Rudolph the Red-Nosed Reindeer; Cricket on the Hearth | 571 |
| 2 | 808 | 1 | Frosty the Snowman; Frosty Returns | 571 |
| 3 | 809 | 1 | Santa Claus is Comin' to Town!; Mr. Magoo's Christmas Carol; The Little Drummer Boy | 571 |
| 4 | 810 | 4 | Tracks 1-7 | 571 |
现在只保留 rn 列中有 1 的那些行：
| rn | MediaID | MediaTypeID | Name | ReleaseID |
|----|---------|-------------|-------------------------------------------------------|-----------|
| 1 | 2 | 2 | Movie | 2 |
| 1 | 12 | 1 | Space Jam; Looney Tunes: Back in Action | 6 |
| 1 | 17 | 3 | Movie | 8 |
| 1 | 620 | 1 | Movie | 463 |
| 1 | 726 | 1 | Movie | 534 |
| 1 | 807 | 1 | Rudolph the Red-Nosed Reindeer; Cricket on the Hearth | 571 |
然后加入 那些行 到 Releases 和 MediaType
宾果
=想要的结果。
不难，真的不难。您真的会想要了解这些 window 功能，因为它们可以解决大量问题。
我有三个 SQL tables：Release（表示电影的发行），Media（表示那些版本；即对于 Blu-ray/DVD 组合，Media 中将有两行，一张蓝光和一张 DVD，指向 Release) 和 [=21 中的同一行=]（定义蓝光、DVD、VHS 等）。 Release/Media 和 MediaType/Media 是一对多的关系，Media 在两者的 "many" 一侧关系。我有一个 Release、vRelease 的视图，其中包含聚合函数，例如显示与该版本关联的媒体数量的 COUNT。到目前为止，这是我对该视图的看法：
SELECT dbo.Release.ReleaseID
,dbo.Release.Name
,CASE WHEN Release.Compilation = 0 THEN 'No' WHEN Release.Compilation = 1 THEN 'Yes' END AS Compilation
,dbo.Release.Owner
,CASE WHEN Release.LentOut = 0 THEN 'No' WHEN Release.LentOut = 1 THEN 'Yes' END AS LentOut
,COUNT(dbo.Media.ReleaseID) AS NumberOfMedia
,MIN(dbo.Media.MediaID) AS FirstMediaID
,MIN(dbo.MediaType.Name) AS FirstMediaType
FROM dbo.MediaType INNER JOIN
dbo.Media ON dbo.MediaType.MediaTypeID = dbo.Media.MediaTypeID RIGHT OUTER JOIN
dbo.Release ON dbo.Media.ReleaseID = dbo.Release.ReleaseID
GROUP BY dbo.Release.ReleaseID, dbo.Release.Name, dbo.Release.Compilation, dbo.Release.Owner, dbo.Release.LentOut
您会注意到我还包含了另外两个聚合列：FirstMediaID 获取与 Media table 中最先出现的版本关联的媒体 ID （即，如果一个发行版有两张与之相关联的 DVD，它会获得一张 ID 值较低的 DVD）。这个专栏本身没有用；然后，我想做的是依次获取与 Media 相关联的 MediaType。换句话说，我想要一个显示第一个 Media 的 MediaType 的列，它附加到每个 Release。之后的列 FirstMediaType 应该这样做，但它却在与 Release 关联的所有 Media 中获取 MediaType 并选择一个按字母顺序排列 - 这意味着 Blu-ray 将始终优先于 DVD（这很好），但音频 CD 将始终优先于其他所有内容（这不好）。
如何获取此视图中的 FirstMediaType 列以获取 FirstMediaID 中标识的媒体的 MediaType？
更新：这里是 tables，它们的列和一些示例行。
来自Release的一对：
+-----------+----------------------------------------+-------+-------------+---------+
| ReleaseID | Name | Owner | Compilation | LentOut |
+-----------+----------------------------------------+-------+-------------+---------+
| 2 | Alice in Wonderland | NULL | 0 | 0 |
| 6 | 4 Film Favorites - Family Comedies | NULL | 1 | 0 |
| 8 | Aladdin | NULL | 0 | 0 |
| 463 | Harry Potter and the Half-Blood Prince | NULL | 0 | 1 |
| 534 | Spirited Away | Ryan | 0 | 0 |
| 571 | The Original Christmas Classics | NULL | 1 | 0 |
+-----------+----------------------------------------+-------+-------------+---------+
Compilation 表示发行版中包含不止一部电影。
Media中对应条目：
+---------+-------------+-------------------------------------------------------------------------------------+-----------+
| MediaID | MediaTypeID | Name | ReleaseID |
+---------+-------------+-------------------------------------------------------------------------------------+-----------+
| 2 | 2 | Movie | 2 |
| 3 | 1 | Movie | 2 |
| 12 | 1 | Space Jam; Looney Tunes: Back in Action | 6 |
| 13 | 1 | Funky Monkey; Osmosis Jones | 6 |
| 17 | 3 | Movie | 8 |
| 620 | 1 | Movie | 463 |
| 726 | 1 | Movie | 534 |
| 807 | 1 | Rudolph the Red-Nosed Reindeer; Cricket on the Hearth | 571 |
| 808 | 1 | Frosty the Snowman; Frosty Returns | 571 |
| 809 | 1 | Santa Claus is Comin' to Town!; Mr. Magoo's Christmas Carol; The Little Drummer Boy | 571 |
| 810 | 4 | Tracks 1-7 | 571 |
+---------+-------------+-------------------------------------------------------------------------------------+-----------+
MediaType中的前几名：
+-------------+--------------+
| MediaTypeID | Name |
+-------------+--------------+
| 1 | DVD Disc |
| 2 | Blu-ray Disc |
| 3 | VHS |
| 4 | Audio CD |
+-------------+--------------+
vRelease中对应的条目应该是这样的：
+-----------+----------------------------------------+-------------+-------+---------+---------------+--------------+----------------+
| ReleaseID | Name | Compilation | Owner | LentOut | NumberOfMedia | FirstMediaID | FirstMediaType |
+-----------+----------------------------------------+-------------+-------+---------+---------------+--------------+----------------+
| 2 | Alice in Wonderland | No | NULL | No | 2 | 2 | Blu-ray Disc |
| 6 | 4 Film Favorites - Family Comedies | Yes | NULL | No | 2 | 12 | DVD Disc |
| 8 | Aladdin | No | NULL | No | 1 | 17 | VHS |
| 463 | Harry Potter and the Half-Blood Prince | No | NULL | Yes | 1 | 620 | DVD Disc |
| 534 | Spirited Away | No | Ryan | No | 1 | 726 | DVD Disc |
| 571 | The Original Christmas Classics | Yes | NULL | No | 4 | 807 | DVD Disc |
+-----------+----------------------------------------+-------------+-------+---------+---------------+--------------+----------------+
但实际上是这样的：
+-----------+----------------------------------------+-------------+-------+---------+---------------+--------------+----------------+
| ReleaseID | Name | Compilation | Owner | LentOut | NumberOfMedia | FirstMediaID | FirstMediaType |
+-----------+----------------------------------------+-------------+-------+---------+---------------+--------------+----------------+
| 2 | Alice in Wonderland | No | NULL | No | 2 | 2 | Blu-ray Disc |
| 6 | 4 Film Favorites - Family Comedies | Yes | NULL | No | 2 | 12 | DVD Disc |
| 8 | Aladdin | No | NULL | No | 1 | 17 | VHS |
| 463 | Harry Potter and the Half-Blood Prince | No | NULL | Yes | 1 | 620 | DVD Disc |
| 534 | Spirited Away | No | Ryan | No | 1 | 726 | DVD Disc |
| 571 | The Original Christmas Classics | Yes | NULL | No | 4 | 807 | Audio CD |
+-----------+----------------------------------------+-------------+-------+---------+---------------+--------------+----------------+
问题出在最后一个。
最简单的方法是在 FirstMediaId = MediaType.MediaId
MediaType table 添加另一个连接
;WITH data AS (
SELECT dbo.Release.ReleaseID
,dbo.Release.Name
,CASE WHEN Release.Compilation = 0 THEN 'No' WHEN Release.Compilation = 1 THEN 'Yes' END AS Compilation
,dbo.Release.Owner
,CASE WHEN Release.LentOut = 0 THEN 'No' WHEN Release.LentOut = 1 THEN 'Yes' END AS LentOut
,COUNT(dbo.Media.ReleaseID) AS NumberOfMedia
,MIN(dbo.Media.MediaID) AS FirstMediaID
FROM dbo.MediaType
INNER JOIN dbo.Media
ON dbo.MediaType.MediaTypeID = dbo.Media.MediaTypeID
RIGHT OUTER JOIN dbo.Release
ON dbo.Media.ReleaseID = dbo.Release.ReleaseID
GROUP BY dbo.Release.ReleaseID, dbo.Release.Name, dbo.Release.Compilation, dbo.Release.Owner, dbo.Release.LentOut
)
SELECT data.ReleaseId
,data.Name
,data.Compilation
,data.Owner
,data.LentOut
,data.NumberOfMedia
,data.FirstMediaId
,MediaType.Name as FirstMediaName
FROM data
LEFT OUTER JOIN dbo.MediaType
ON data.FirstMediaId = MediaType.MediaTypeId
returns整行与"First"、"Last"、"Earliest"、"Latest"等需求相关联的一个非常方便的技术是使用row_number() over()。这里你想要"first media type"，所以它在这里是相关的。
正如您将在以下查询中看到的那样，加入 [Media] table 被替换为包含行号计算的子查询。这里我们partition byReleaseID和order byMediaID，所以，对于each ReleaseID 第一行将是具有最低 MediaID 值的行。然后在这个派生的 table 的连接中添加一个额外的条件以仅考虑行号为 1.
建议查询
SELECT
r.ReleaseID
, m.MediaID
, mt.MediaTypeID
, mt.name MediaName
, r.Name
, CASE
WHEN r.Compilation = 0 THEN 'No'
WHEN r.Compilation = 1 THEN 'Yes'
END AS compilation
, r.Owner
, CASE
WHEN r.LentOut = 0 THEN 'No'
WHEN r.LentOut = 1 THEN 'Yes'
END AS lentout
FROM dbo.Release r
INNER JOIN (
SELECT
Media.*
, ROW_NUMBER() OVER(PARTITION BY ReleaseID
ORDER BY MediaID) AS rn
FROM dbo.Media
) m ON r.ReleaseID = m.ReleaseID and rn = 1
INNER JOIN dbo.MediaType mt ON m.MediaTypeID = mt.MediaTypeID
结果
| ReleaseID | MediaID | MediaTypeID | MediaName | Name | compilation | Owner | lentout |
|-----------|---------|-------------|--------------|----------------------------------------|-------------|--------|---------|
| 2 | 2 | 2 | Blu-ray Disc | Alice in Wonderland | No | (null) | No |
| 6 | 12 | 1 | DVD Disc | 4 Film Favorites - Family Comedies | Yes | (null) | No |
| 8 | 17 | 3 | VHS | Aladdin | No | (null) | No |
| 463 | 620 | 1 | DVD Disc | Harry Potter and the Half-Blood Prince | No | (null) | Yes |
| 534 | 726 | 1 | DVD Disc | Spirited Away | No | Ryan | No |
| 571 | 807 | 1 | DVD Disc | The Original Christmas Classics | Yes | (null) | No |
我最终找到了一种简单的方法来做我想做的事。它不像 Used_By_Already 的答案那么花哨（据我所知，它确实有效）并且可能在某处打破了 SQL 最佳实践规则，但它更容易理解和保持——至少对我的新手来说是这样。
由于问题是试图让视图使用它在连接中计算的聚合列，我只是将两步操作拆分为两个视图。 vReleasePre 包含我在原始查询中概述的所有列，FirstMediaType 除外。 vRelease 现在只需从 vReleasePre 中获取所有列并添加 FirstMediaType，它从末尾的连接中获取其值：LEFT OUTER JOIN dbo.vMedia ON dbo.vReleasePre.FirstMediaID = dbo.vMedia.MediaID，其中 vMedia 是包含 Media 中所有列的视图，加上 MediaType 列（我已经有 vMedia 了）。
由于此数据库通过 Entity Framework 在 ASP.NET MVC 网络应用程序中使用，并且 EF 对数据模型将接受和不接受的内容一直很奇怪，我想一个简单但迂回的解决方案可能是我的最佳选择。
vReleasePre:
SELECT dbo.Release.ReleaseID
,dbo.Release.Name
,CASE WHEN Release.Compilation = 0 THEN 'No' WHEN Release.Compilation = 1 THEN 'Yes' END AS Compilation
,dbo.Release.Owner
,CASE WHEN Release.LentOut = 0 THEN 'No' WHEN Release.LentOut = 1 THEN 'Yes' END AS LentOut
,COUNT(dbo.Media.ReleaseID) AS NumberOfMedia
,MIN(dbo.Media.MediaID) AS FirstMediaID
FROM dbo.MediaType INNER JOIN
dbo.Media ON dbo.MediaType.MediaTypeID = dbo.Media.MediaTypeID RIGHT OUTER JOIN
dbo.Release ON dbo.Media.ReleaseID = dbo.Release.ReleaseID
GROUP BY dbo.Release.ReleaseID, dbo.Release.Name, dbo.Release.Compilation, dbo.Release.Owner, dbo.Release.LentOut
vRelease:
SELECT dbo.vReleasePre.ReleaseID
,dbo.vReleasePre.Name
,dbo.vReleasePre.Compilation
,dbo.vReleasePre.Owner
,dbo.vReleasePre.LentOut
,dbo.vReleasePre.NumberOfMedia
,dbo.vMedia.MediaType
FROM dbo.vReleasePre LEFT OUTER JOIN
dbo.vMedia ON dbo.vReleasePre.FirstMediaID = dbo.vMedia.MediaID
对于新手来说，这是我使用的子查询
SELECT
ROW_NUMBER() OVER(PARTITION BY ReleaseID
ORDER BY MediaID) AS rn
, Media.*
FROM dbo.Media
这就是它的作用（参见 rn 列）
| rn | MediaID | MediaTypeID | Name | ReleaseID |
|----|---------|-------------|-------------------------------------------------------------------------------------|-----------|
| 1 | 2 | 2 | Movie | 2 |
| 2 | 3 | 1 | Movie | 2 |
| 1 | 12 | 1 | Space Jam; Looney Tunes: Back in Action | 6 |
| 2 | 13 | 1 | Funky Monkey; Osmosis Jones | 6 |
| 1 | 17 | 3 | Movie | 8 |
| 1 | 620 | 1 | Movie | 463 |
| 1 | 726 | 1 | Movie | 534 |
| 1 | 807 | 1 | Rudolph the Red-Nosed Reindeer; Cricket on the Hearth | 571 |
| 2 | 808 | 1 | Frosty the Snowman; Frosty Returns | 571 |
| 3 | 809 | 1 | Santa Claus is Comin' to Town!; Mr. Magoo's Christmas Carol; The Little Drummer Boy | 571 |
| 4 | 810 | 4 | Tracks 1-7 | 571 |
现在只保留 rn 列中有 1 的那些行：
| rn | MediaID | MediaTypeID | Name | ReleaseID |
|----|---------|-------------|-------------------------------------------------------|-----------|
| 1 | 2 | 2 | Movie | 2 |
| 1 | 12 | 1 | Space Jam; Looney Tunes: Back in Action | 6 |
| 1 | 17 | 3 | Movie | 8 |
| 1 | 620 | 1 | Movie | 463 |
| 1 | 726 | 1 | Movie | 534 |
| 1 | 807 | 1 | Rudolph the Red-Nosed Reindeer; Cricket on the Hearth | 571 |
然后加入 那些行 到 Releases 和 MediaType
宾果
=想要的结果。
不难，真的不难。您真的会想要了解这些 window 功能，因为它们可以解决大量问题。