T-SQL - string concatenation

问题

Hope someone can help - I am a novice SQL hacker (and very bad at it indeed!)

I have two tables on SQL Server 2005 TABLE 1 and TABLE2:

TABLE1

COL1         COL2
1            10
2            20
3            30
4            10
4            20
5            20
6            30
7            10
7            20

TABLE2

COL1         COL2
10            A
20            B
30            C

COL2 in TABLE2 is a character representation of the numerical data in COL2 TABLE1. I hope this is understandable?

I have worked out how to select COL1 and COL2 from TABLE1 and concatenate the results to show this:

COL1         COL2Concat
1            10
2            20
3            30
4            10, 20
5            20
6            30
7            10, 20, 30 

Using this:

SELECT  COL1,
        STUFF(( SELECT  ',' + CAST(a.COL2 AS VARCHAR(255)) AS [text()]
                FROM    TABLE1 a
                WHERE   a.COL1 = b.COL1
                ORDER BY a.COL2
              FOR
                XML PATH('')
              ), 1, 1, '') AS COL2Concat
FROM    TABLE1 b
GROUP BY COL1
ORDER BY COL1

But now I'd like to try and get the same result except use the data in COL2 TABLE2... i.e.:

COL1         COL2Concat
1            A
2            B
3            C
4            A, B
5            B
6            C
7            A, B, C 

Any ideas - I'm stuck to be honest as I have tried modifying the STUFF query, but it never seems to come out right...

回答1:

you could try...

SELECT  COL1,
        STUFF(( SELECT  ',' + CAST((SELECT COL2
                                        FROM TABLE2
                                        WHERE TABLE2.COL1 = a.COL1) AS VARCHAR(255)) AS [text()]
                FROM    TABLE1 a
                WHERE   a.COL1 = b.COL1
                ORDER BY a.COL2
              FOR
                XML PATH('')
              ), 1, 1, '') AS COL2Concat
FROM    TABLE1 b
GROUP BY COL1
ORDER BY COL1

来源：https://stackoverflow.com/questions/3373100/t-sql-string-concatenation