SQL Server 连接 GROUP BY [英] SQL Server Concatenate GROUP BY

问题描述

我有一个类似这样的查询

I have a query that looks like this

SELECT J.JobID,T.Title FROM JobsTagMap J
Left Join Tags T
ON J.TagID=T.TagID

即返回如下数据集(简而言之，JobID实际上是一个UniqueIdentifier)

That returns the following dataset (simplified, JobID is actually a UniqueIdentifier)

JobID    Title
1        Tag1
1        Tag2
2        Tag2
2        Tag5
2        Tag9

现在，我想通过 JobID 列对其进行分组并连接标题，因此结果如下

Now, i'd like to group this by the JobID-column and concatenate the Title, so the results is as following

JobID    Title
1        Tag1,Tag2
2        Tag2,Tag5,Tag9

我该怎么做?

推荐答案

如果您使用的是 sql server 2005+.然后你可以这样做:

If you are using sql server 2005+. Then you can do like this:

SELECT 
    JobsTagMap.JobID,
    STUFF
    (
        (
            SELECT 
                ',' +Title
            FROM
                Tags
            WHERE
                Tags.TagID=JobsTagMap.TagID
            FOR XML PATH('')
        )
    ,1,1,'') AS Title
FROM JobsTagMap

编辑

因为您没有向我们展示表结构和不同表中的数据.这有点难知道.所以我假设你的表结构看起来像这样:

Because you did not show us the table structure and the data in the different tables. It was a lite bit hard to know. So I assume that your table structure looks something like this:

CREATE TABLE JobsTagMap
(
    JobID INT,
    TagID INT
)

CREATE TABLE Tags
(
    TagID INT,
    Title VARCHAR(100)
)

使用这些数据:

INSERT INTO JobsTagMap
VALUES(1,1),(1,2),(2,2),(2,4),(2,5)

INSERT INTO Tags
VALUES(1,'Tag1'),(2,'Tag2'),(3,'Tag2'),(4,'Tag5'),(5,'Tag9')

如果您正在获取数据，则您显示的 JobID 不能是唯一的.您可能在它唯一的某处有一个 Job 表.如果您只想使用您显示的这些表格，那么您需要执行以下操作:

If you are getting that data that you are showing the JobID cannot be unique. You might have the a Job table somewhere where it is unique. If you just want to use these table that you are showing then you need to do something like this:

;WITH CTE
AS
(
    SELECT
        ROW_NUMBER() OVER(PARTITION BY JobID ORDER BY JobID) AS RowNbr,
        JobsTagMap.*
    FROM
        JobsTagMap
)
SELECT
    *,
    STUFF
    (
        (
            SELECT 
                ',' +Title
            FROM
                Tags
                JOIN JobsTagMap
                    ON Tags.TagID=JobsTagMap.TagID
            WHERE
                JobsTagMap.JobID=CTE.JobID
            FOR XML PATH('')
        )
    ,1,1,'') AS Title
FROM
    CTE
WHERE
    CTE.RowNbr=1

这会让你得到这个结果:

This will get you this result:

1   1   1   Tag1,Tag2
1   2   2   Tag2,Tag5,Tag9

所以以后总是显示什么表结构和它数据.那会给你更好的答案

So in the future always show what table structure and it data. That will give you better answers

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