SQL Server Concatenate GROUP BY

问题:

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 

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

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

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 

How would i do that?

回答1:

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 

EDIT

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) ) 

With this data:

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') 

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 

This will get you this result:

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

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

回答2:

I use a scalar function for exactly that. There are going to be some purist that decry should never use a row based operation but hey this works and if you are only returning a few rows then response time is fine.

CREATE FUNCTION [dbo].[JoinMVText]  (    @sID int,    @fieldID tinyint  )  RETURNS VARCHAR(MAX)  AS   BEGIN     DECLARE @MVtextList varchar(max)     SELECT @MVtextList = COALESCE(@MVtextList + '; ', '') + docMVtext.value     FROM docMVtext with (nolock)      WHERE docMVtext.sID = @sID and fieldID = @fieldID     RETURN @MVtextList  END 

文章来源: SQL Server Concatenate GROUP BY