How to concatenate text from multiple rows into a single text string in SQL server?
Consider a database table holding names, with three rows:
Peter
Paul
Mary
Is there an easy way to turn this into a single string of Peter, Paul, Mary ?
I had a similar issue when I was trying to join two tables with one-to-many relationships. In SQL 2005 I found that XML PATH method can handle the concatenation of the rows very easily.
If there is a table called STUDENTS
SubjectID StudentName
---------- -------------
1 Mary
1 John
1 Sam
2 Alaina
2 Edward
Result I expected was:
SubjectID StudentName
---------- -------------
1 Mary, John, Sam
2 Alaina, Edward
I used the following T-SQL :
Select Main.SubjectID,
Left(Main.Students,Len(Main.Students)-1) As "Students"
From
(
Select distinct ST2.SubjectID,
(
Select ST1.StudentName + ',' AS [text()]
From dbo.Students ST1
Where ST1.SubjectID = ST2.SubjectID
ORDER BY ST1.SubjectID
For XML PATH ('')
) [Students]
From dbo.Students ST2
) [Main]
You can do the same thing in a more compact way if you can concat the commas at the beginning and use substring to skip the first one so you don't need to do a sub-query:
Select distinct ST2.SubjectID,
substring(
(
Select ','+ST1.StudentName AS [text()]
From dbo.Students ST1
Where ST1.SubjectID = ST2.SubjectID
ORDER BY ST1.SubjectID
For XML PATH ('')
), 2, 1000) [Students]
From dbo.Students ST2
This answer may return unexpected results when an ORDER BY clause is present. For consistent results, use one of the FOR XML PATH methods detailed in other answers.
Use COALESCE :
DECLARE @Names VARCHAR(8000)
SELECT @Names = COALESCE(@Names + ', ', '') + Name
FROM People
Just some explanation (since this answer seems to get relatively regular views):
1) No need to initialize @Names with an empty string value.
2) No need to strip off an extra separator at the end.
@Names NULL after that row, and the next row will start over as an empty string again. Easily fixed with one of two solutions: DECLARE @Names VARCHAR(8000)
SELECT @Names = COALESCE(@Names + ', ', '') + Name
FROM People
WHERE Name IS NOT NULL
or:
DECLARE @Names VARCHAR(8000)
SELECT @Names = COALESCE(@Names + ', ', '') +
ISNULL(Name, 'N/A')
FROM People
Depending on what behavior you want (the first option just filters NULLs out, the second option keeps them in the list with a marker message [replace 'N/A' with whatever is appropriate for you]).
One method not yet shown via the XML data() command in MS SQL Server is:
Assume table called NameList with one column called FName,
SELECT FName + ', ' AS 'data()'
FROM NameList
FOR XML PATH('')
returns:
"Peter, Paul, Mary, "
Only the extra comma must be dealt with.
Edit: As adopted from @NReilingh's comment, you can use the following method to remove the trailing comma. Assuming the same table and column names:
STUFF(REPLACE((SELECT '#!' + LTRIM(RTRIM(FName)) AS 'data()' FROM NameList
FOR XML PATH('')),' #!',', '), 1, 2, '') as Brands
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