SQL Server: combining multiple rows into one row

Question

I have a SQL query like this;

SELECT * 
FROM Jira.customfieldvalue
WHERE CUSTOMFIELD = 12534
AND ISSUE = 19602

And that's the results;

What I want is; showing in one row (cell) combined all STRINGVALUE's and they are separated with a comma. Like this;

SELECT --some process with STRINGVALUE--
FROM Jira.customfieldvalue
WHERE CUSTOMFIELD = 12534
AND ISSUE = 19602

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E-Maili, Proforma Fatura

How can I do that?

Solution 1

There are several methods.

If you want just the consolidated string value returned, this is a good quick and easy approach

DECLARE @combinedString VARCHAR(MAX)
SELECT @combinedString = COALESCE(@combinedString + ', ', '') + stringvalue
FROM jira.customfieldValue
WHERE customfield = 12534
    AND ISSUE = 19602

SELECT @combinedString as StringValue 

Which will return your combined string.

You can also try one of the XML methods e.g.

SELECT DISTINCT Issue, Customfield, StringValues
FROM Jira.customfieldvalue v1
CROSS APPLY ( SELECT StringValues + ',' 
              FROM jira.customfieldvalue v2
              WHERE v2.Customfield = v1.Customfield 
                  AND v2.Issue = v1.issue 
              ORDER BY ID 
                  FOR XML PATH('') )  D ( StringValues )
WHERE customfield = 12534
    AND ISSUE = 19602

Solution 2

You can achieve this is to combine For XML Path and STUFF as follows:

SELECT (STUFF((
        SELECT ', ' + StringValue
        FROM Jira.customfieldvalue
        WHERE CUSTOMFIELD = 12534
        AND ISSUE = 19602
        FOR XML PATH('')
        ), 1, 2, '')
    ) AS StringValue

Solution 3

There's a convenient method for this in MySql called GROUP_CONCAT. An equivalent for SQL Server doesn't exist, but you can write your own using the SQLCLR. Luckily someone already did that for you.

Your query then turns into this (which btw is a much nicer syntax):

SELECT CUSTOMFIELD, ISSUE, dbo.GROUP_CONCAT(STRINGVALUE)
FROM Jira.customfieldvalue
WHERE CUSTOMFIELD = 12534 AND ISSUE = 19602
GROUP BY CUSTOMFIELD, ISSUE

But please note that this method is good for at the most 100 rows within a group. Beyond that, you'll have major performance problems. SQLCLR aggregates have to serialize any intermediate results and that quickly piles up to quite a lot of work. Keep this in mind!

Interestingly the FOR XML doesn't suffer from the same problem but instead uses that horrendous syntax.

Solution 4

This is an old question, but as of the release of Microsoft SQL Server 2017 you can now use the STRING_AGG() function which is much like the GROUP_CONCAT function in MySQL.

STRING_AGG (Transact-SQL) Documentation

Example

USE AdventureWorks2016
GO
SELECT STRING_AGG (CONVERT(NVARCHAR(max),FirstName), ',') AS csv 
FROM Person.Person; 

Returns

Syed,Catherine,Kim,Kim,Kim,Hazem

Solution 5

I believe for databases which support listagg function, you can do:

select id, issue, customfield, parentkey, listagg(stingvalue, ',') within group (order by id)
from jira.customfieldvalue
where customfield = 12534 and issue = 19602
group by id, issue, customfield, parentkey

View more solutions

Comments

[Soner Gönül]

Thanks but sorry, my question was for "T-SQL" as you can see. Your answer was also included in Combine Multiple child rows into one row MYSQL by the way.

[Christian]

I have a situation where this will only group two or three rows at max, so this is perfect for me in its simplicity. Seeing as this answer is a few years old, has performance of this method improved?

[Thomas Gak-Deluen]

There is a very good tutorial here mssqltips.com/sqlservertip/2914/…

[Jan]

If you are going to run this query from PHP, be sure to declare the @combinedstring as fixed length varchar: DECLARE @combinedString VARCHAR(255)

[mehrab habibi]

I think use STUFF and FOR XML is the better way to solve the problem

[Fütemire]

I know this was posted in 2011, but as of SQL 2017 you can now use the STRING_AGG() function, which is like MySQL GROUP_CONCAT() is you want to update your answer. ;)