Question

I’m stuck on an aggregation problem that I can’t get to the bottom of.

I have some data which is best summarized as follows

id |phraseId|seqNum|word
=========================
1  |1       |1     |hello
2  |1       |2     |world
3  |2       |1     |black
4  |2       |2     |and
5  |2       |3     |white

I’d like a query that gives back the following data:

phraseId|completePhrase
========================
1       |hello world
2       |black and white

Anyone?

EDIT

I notice all the provided solutions use FOR XML PATH. What is this magic?

Answer 1

One solution is to create an UDF using an FOR XML PATH expression.

• the UDF handles the concatenation of one PhraseID
• it can be used in a normal select

SQL Statement

SELECT  PhraseID, dbo.UDF_ConcatWord(PhraseID)
FROM    Phrases
GROUP BY PhraseID

Creating the UDF

CREATE FUNCTION dbo.UDF_ConcatWord(@phraseID INT) RETURNS VARCHAR(8000) AS
BEGIN  
  DECLARE @r VARCHAR(8000)
  SELECT @r = (
    SELECT  word + ', '
    FROM    Phrases
    WHERE   phraseID = @phraseID
    FOR XML PATH('')
  )
  IF LEN(@r) > 0 SET @r = SUBSTRING(@r, 1, LEN(@r)-1)
  RETURN @r
END
GO

edit

After revising some of the links myself, an even shorter solution is

SQL Statement

SELECT  DISTINCT p1.PhraseID
        , STUFF(( SELECT  ' ' + p2.word 
                  FROM    Phrases AS p2 
                  WHERE   p2.PhraseID = p1.PhraseID 
                  FOR XML PATH('')), 1, 1, '') AS completePhrase
FROM      Phrases AS p1
ORDER BY  p1.PhraseID