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?

20 upvote
  flag
For answers specific to SQL Server, try this question. – Matt Hamilton
12 upvote
  flag
For MySQL, check out Group_Concat from this answer – Pykler
19 upvote
  flag
I wish the next version of SQL Server would offer a new feature to solve multi-row string concatination elegantly without the silliness of FOR XML PATH. – Pete Alvin
upvote
  flag
step by step tutorial for describe above answers : try this article : [ sqlmatters.com/Articles/… ] – saber tabatabaee yazdi
2 upvote
  flag
Not SQL, but if this is a once-only thing, you can paste the list into this in-browser tool convert.town/column-to-comma-separated-list – Stack Man
upvote
  flag
In Oracle you can use the LISTAGG(COLUMN_NAME) from 11g r2 before that there is an unsupported function called WM_CONCAT(COLUMN_NAME) which does the same. – Richard

39 Answers 11

Depends on your database vendor. MySQL has concat_ws. MS SQL Server expects you to do it in your client application.

Update: you could also do it in an external procedure or UDF, perhaps by using a cursor or calling out to CLR code.

upvote
  flag
@Joel, the funciton in MySQL is CONCAT_WS(), but it's only useful for 1 row within a result. – Darryl Hein

One way you could do it in SQL Server would be to return the table content as XML (for XML raw), convert the result to a string and then replace the tags with ", ".

In MySQL there is a function, GROUP_CONCAT(), which allows you to concatenate the values from multiple rows. Example:

SELECT 1 AS a, GROUP_CONCAT(name ORDER BY name ASC SEPARATOR ', ') AS people 
FROM users 
WHERE id IN (1,2,3) 
GROUP BY a
2 upvote
  flag
Used to love this one, have not seen a alternative to this function with any other Db yet! – Binoj Antony
1 upvote
  flag
This totally solved my problem. I was trying to pull all the payment dates for a given charge on an account, this solved it perfectly. Thanks! – Maximus
upvote
  flag
works well. But when i use SEPARATOR '", "' i'll miss some chars at the end of the last entry. why can this happen? – gooleem
upvote
  flag
@gooleem I'm not clear on what you mean, but this function only puts the separator between items, not after. If that's not the answer, I'd recommend posting a new question. – Darryl Hein
upvote
  flag
@DarrylHein for my needs i used the separator as above. But this cuts me some chars at the very end of the output. This is very strange and seems to be a bug. I dont have a solution, i just workedaround. – gooleem

I don't have access to a SQL Server at home, so I'm guess at the syntax here, but it's more or less:

DECLARE @names VARCHAR(500)

SELECT @names = @names + ' ' + Name
FROM Names
6 upvote
  flag
You'd need to init @names to something non-null, otherwise you will get NULL throughout; you'd also need to handle the delimiter (including the unnecessary one) – Marc Gravell
2 upvote
  flag
the only problem with this approach (which i use all the time) is that you can't embed it – ekkis
upvote
  flag
To get rid of the leading space change the query to SELECT @names = @names + CASE WHEN LEN(@names)=0 THEN '' ELSE ' ' END + Name FROM Names – Tian van Heerden
upvote
  flag
Also, you have to check that Name is not null, you can do it by doing: SELECT @names = @names + ISNULL(' ' + Name, '') – Vita1ij

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):

  • Coalesce is really just a helpful cheat that accomplishes two things:

1) No need to initialize @Names with an empty string value.

2) No need to strip off an extra separator at the end.

  • The solution above will give incorrect results if a row has a NULL Name value (if there is a NULL, the NULL will make @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]).

57 upvote
  flag
To be clear, coalesce has nothing to do with creating the list, it just makes sure that NULL values are not included. – Graeme Perrow
14 upvote
  flag
@Graeme Perrow It doesn't exclude NULL values (a WHERE is required for that -- this will lose results if one of the input values is NULL), and it is required in this approach because: NULL + non-NULL -> NULL and non-NULL + NULL -> NULL; also @Name is NULL by default and, in fact, that property is used as an implicit sentinel here to determine if a ', ' should be added or not. – user166390
upvote
  flag
Two ways to fix this to gracefully ignore NULLs: Either SELECT @Names = @Names + ', ' + Name FROM People WHERE Name IS NOT NULL or else SELECT @Names = COALESCE(@Names + ', ' + Name, @Names) FROM People. – krubo
4 upvote
  flag
@krubo No, the problem is that @Names = @Names + *anything* will be null because @Names is null upon declaration. The COALESCE resolves both null Name values and the initial null @Names value. – Kirk Broadhurst
upvote
  flag
This doesn't work for data types varchar and ntext, as they're both incompatible with the add operator. – XpiritO
upvote
  flag
@XpiritO - do you mean text and ntext? Varchar is compatible; text and ntext could be converted (if you are on SQL 2005 convert them to VARCHAR(MAX)/NVARCHAR(MAX) and you don't lose anything; Otherwise you'll have to accept the possibility of truncation anyway, since you can't declare a text/ntext variable). – Chris Shaffer
51 upvote
  flag
Please note that this method of concatenation relies on SQL Server executing the query with a particular plan. I have been caught out using this method (with the addition of an ORDER BY). When it was dealing with a small number of rows it worked fine but with more data SQL Server chose a different plan which resulted in selecting the first item with no concatenation whatsoever. See this article by Anith Sen. – fbarber
12 upvote
  flag
This method cannot be used as a sub query in a select list or where-clause, because it use a tSQL variable. In such cases you could use the methods offered by @Ritesh – R. Schreurs
1 upvote
  flag
This solution will not work in a view but Ritesh's one would. – Shinigamae
upvote
  flag
This is the simplest way to build dynamic SQL if you want to apply the same command to many objects. Cade Roux uses it to rename schemas, and I use it to rename tSQLt test classes. Thanks, Chris! – Iain Elder
upvote
  flag
Tried this, loved it at first because of how simple and brilliant it is. But like any other repetitive concat process to a varchar(), I/O and CPU eventually peg. For 20,000 GUIDs, it took 2 minutes to concatenate them, whereas using the for xml path('') took less than 1 second. – James L.
upvote
  flag
How to add Distinct to it if i only want to add up distinct values ? – confusedMind
1 upvote
  flag
@confusedMind - like this: DECLARE @Names VARCHAR(8000) SELECT @Names = COALESCE(@Names + ', ', '') + Name FROM ( SELECT DISTINCT Name FROM People ) – Shay Nissel
7 upvote
  flag
This is not a reliable method of concatenation. It is unsupported and should not be used (per Microsoft, e.g. support.microsoft.com/en-us/kb/287515, connect.microsoft.com/SQLServer/Feedback/Details/704389). It can change without warning. Use the XML PATH technique discussed in //allinonescript.com/questions/5031204/… I wrote more here: marc.durdin.net/2015/07/… – Marc Durdin
1 upvote
  flag
A Major problem with this approach is that it would truncate all values which are over 8000. – Nezam
upvote
  flag
Your explanation doesn't really explain what this does. It's relying on SQL Server executing the expression for every row. That'd be nifty if it can be relied on. But see other comments indicating that SQL Server is not required to do so for this type of query. – binki
upvote
  flag
I found the same exact code example here (posted 6 months before): codeproject.com/Tips/334400/… I think a reference to the author should be due. – Leonardo Spina
upvote
  flag
Darn. I upvoted this answer but now that I know that it isn't the correct way to do concatenation because it can screw you over since it is an unsupported feature I can't remove my upvote anymore :-( Now I have misled many. – Jon49
upvote
  flag
The solution works fine; however, it truncates the text at lenght 65576 – BI Dude
DECLARE @Names VARCHAR(8000)
SELECT @name = ''
SELECT @Names = @Names + ',' + Names FROM People
SELECT SUBSTRING(2, @Names, 7998)

This puts the stray comma at the beginning.

However, if you need other columns, or to CSV a child table you need to wrap this in a scalar user defined field (UDF).

You can use XML path as a correlated subquery in the SELECT clause too (but I'd have to wait until I go back to work because Google doesn't do work stuff at home :-)

up vote 1018 down vote accepted

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 subquery:

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
1 upvote
  flag
I recieve an error "Incorrect syntax near the keyword 'For'" running MS SQL Server 2008 R2 – Menefee
9 upvote
  flag
Great solution. The following may be helpful if you need to handle special characters like those in HTML: Rob Farley: Handling special characters with FOR XML PATH(''). – user140628
upvote
  flag
What if there is no 'Subject ID' – JsonStatham
7 upvote
  flag
Apparently this doesn't work if the names contain XML characters such as < or &. See @BenHinman's comment. – Sam
upvote
  flag
This is a good solution. I concatenated 20,000 GUIDs with it in less than 1 second. for xml path('') performs far better than any type cursor and/or variable concat approach. – James L.
14 upvote
  flag
NB: This method is reliant on undocumented behavior of FOR XML PATH (''). That means it should not be considered reliable as any patch or update could alter how this functions. It's basically relying on a deprecated feature. – Bacon Bits
upvote
  flag
@Bacon Bits - Could you explain that a bit more? It's an incredibly widely used piece of code. – Whelkaholism
1 upvote
  flag
@Whelkaholism That was Microsoft's initial response to this query. I can't seem to find their initial statement anymore (as you said, it's very widely used), but for many years after Server 2005 the SQL Server team maintained that FOR XML PATH ('') combined with unnamed columns has undefined behavior (i.e., the behavior is not in the design spec). Even on 2014, you will not see FOR XML PATH ('') used with unnamed columns in the SQL Server doc. FOR XML PATH with unnamed columns, yes. FOR XML PATH ('') with named columns, yes. But those generate different results. – Bacon Bits
16 upvote
  flag
@Whelkaholism The bottom line is that FOR XML is intended to generate XML, not concatenate arbitrary strings. That's why it escapes &, < and > to XML entity codes (&amp;, &lt;, &gt;). I assume it also will escape " and ' to &quot; and &apos; in attributes as well. It's not GROUP_CONCAT(), string_agg(), array_agg(), listagg(), etc. even if you can kind of make it do that. We should be spending our time demanding Microsoft implement a proper function. – Bacon Bits
upvote
  flag
I've to use AS 'data()' insted AS [text()]. – paio
1 upvote
  flag
@BaconBits This answer uses better syntax which deals with special characters better by using the TYPE keyword and extracting the contents using the value XML function. Using that method, you can even use tag names and create well formed XML. But you needn't fear columns without names. They are officially supported at least as early as SQL Server 2008. – Riley Major
1 upvote
  flag
To remove the initial comma, I usually use ROW_NUMBER(). Complete sample in an answer below. CASE ROW_NUMBER() OVER (ORDER BY stu.Name) WHEN 1 THEN '' ELSE ', ' END + stu.Name – Graeme
1 upvote
  flag
Good news: MS SQL Server will be adding string_agg in v.Next. and all of this can go away. – Jason C
upvote
  flag
Added an improved example to address the issue pointed out by @Sam, characters <, > and & being returned as xml escape sequences &lt;, &gt; and &amp;. – rrozema
upvote
  flag
You can use STUFF instead of SUBSTRING to remove the leading comma. – Jamie Kitson

In SQL Server 2005 ...

SELECT Stuff(
  (SELECT N', ' + Name FROM Names FOR XML PATH(''),TYPE)
  .value('text()[1]','nvarchar(max)'),1,2,N'')

In [SQL Server 2016]

you can use the FOR JSON syntax

https://docs.microsoft.com/en-us/sql/t-sql/queries/select-for-clause-transact-sql

i.e.

SELECT per.ID,
Emails = JSON_VALUE(
   REPLACE(
     (SELECT _ = em.Email FROM Email em WHERE em.Person = per.ID FOR JSON PATH)
    ,'"},{"_":"',', '),'$[0]._'
) 
FROM Person per

And the result will become

Id  Emails
1   abc@gmail.com
2   NULL
3   def@gmail.com, xyz@gmail.com

This will work even your data contains invalid XML characters

the '"},{"":"' is safe because if you data contain '"},{"":"', it will be escaped to "},{\"_\":\"

You can replace ', ' with any string separator


And in [SQL Server 2017]

You can use the new STRING_AGG function

https://docs.microsoft.com/en-us/sql/t-sql/functions/string-agg-transact-sql

3 upvote
  flag
Good use of the STUFF function to nix the leading two characters. – David
3 upvote
  flag
I like this solution best, because I can easily use it in a select list by appending 'as <label>'. I am not sure how to do this with the solution of @Ritesh. – R. Schreurs
11 upvote
  flag
This is better than the accepted answer because this option also handles un-escaping XML reserverd characters such as <, >, &, etc. which FOR XML PATH('') will automatically escape. – BateTech

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
9 upvote
  flag
holy s**t thats amazing! When executed on its own, as in your example the result is formatted as a hyperlink, that when clicked (in SSMS) opens a new window containing the data, but when used as part of a larger query it just appears as a string. Is it a string? or is it xml that i need to treat differently in the application that will be using this data? – Ben
7 upvote
  flag
This approach also XML-escapes characters like < and >. So, SELECTing '<b>' + FName + '</b>' results in "&lt;b&gt;John&lt;/b&gt;&lt;b&gt;Paul..." – Lukáš Lánský
7 upvote
  flag
Neat solution. I am noticing that even when I do not add the + ', ' it still adds a single space between every concatenated element. – Baodad
upvote
  flag
Seems like the fastest solution. I did not test it and have no metrics available sorry. – JP Hellemons
upvote
  flag
Neat! Any ideas on how to deal with the comma at the end? – slayernoah
upvote
  flag
Super answer! No deal with stored procedures! – Konstantin
5 upvote
  flag
@Baodad That appears to be part of the deal. You can workaround by replacing on an added token character. For example, this does a perfect comma-delimited list for any length: SELECT STUFF(REPLACE((SELECT '#!'+city AS 'data()' FROM #cityzip FOR XML PATH ('')),' #!',', '),1,2,'') – NReilingh
upvote
  flag
Haha, but at that point you might as well just not use data() in the first place and just do one of the examples above. It seems data() is really just a shorthand for "space delimit this" and if you want something else it's useless -- unless there's a performance impact. – NReilingh
1 upvote
  flag
Wow, actually in my testing using data() and a replace is WAY more performant than not. Super weird. – NReilingh
upvote
  flag
If you replace data() with text() it seems to generate the list without the need to trim spaces out. – illmortem
upvote
  flag
Incredible!!!!! this should be the accepted answer! – ciosoriog

Using XML helped me in getting rows separated with commas. For the extra comma we can use the replace function of SQL Server. Instead of adding a comma, use of the AS 'data()' will concatenate the rows with spaces, which later can be replaced with commas as the syntax written below.

REPLACE(
        (select FName AS 'data()'  from NameList  for xml path(''))
         , ' ', ', ') 
2 upvote
  flag
This is the best answer here in my opinon. The use of declare variable is no good when you need to join in another table, and this is nice and short. Good work. – David Roussel
4 upvote
  flag
that's not working good if FName data has spaces already, for example "My Name" – binball
upvote
  flag
Really it is working for me on ms-sql 2016 Select REPLACE( (select Name AS 'data()' from Brand Where Id IN (1,2,3,4) for xml path('')) , ' ', ', ') as allBrands – Rejwanul Reza

How about this:

   ISNULL(SUBSTRING(REPLACE((select ',' FName as 'data()' from NameList for xml path('')), ' ,',', '), 2, 300), '') 'MyList'

Where the "300" could be any width taking into account the max number of items you think will show up.

In Oracle, it is wm_concat. I believe this function is available in the 10g release and higher.

I usually use select like this to concatenate strings in SQL Server:

with lines as 
( 
  select 
    row_number() over(order by id) id, -- id is a line id
    line -- line of text.
  from
    source -- line source
), 
result_lines as 
( 
  select 
    id, 
    cast(line as nvarchar(max)) line 
  from 
    lines 
  where 
    id = 1 
  union all 
  select 
    l.id, 
    cast(r.line + N', ' + l.line as nvarchar(max))
  from 
    lines l 
    inner join 
    result_lines r 
    on 
      l.id = r.id + 1 
) 
select top 1 
  line
from
  result_lines
order by
  id desc

In SQL Server 2005 and later, use the query below to concatenate the rows.

DECLARE @t table
(
    Id int,
    Name varchar(10)
)
INSERT INTO @t
SELECT 1,'a' UNION ALL
SELECT 1,'b' UNION ALL
SELECT 2,'c' UNION ALL
SELECT 2,'d' 

SELECT ID,
stuff(
(
    SELECT ','+ [Name] FROM @t WHERE Id = t.Id FOR XML PATH('')
),1,1,'') 
FROM (SELECT DISTINCT ID FROM @t ) t
2 upvote
  flag
I believe this fails when the values contain XML symbols such as < or &. – Sam

If you want to deal with nulls you can do it by adding a where clause or add another COALESCE around the first one.

DECLARE @Names VARCHAR(8000) 
SELECT @Names = COALESCE(COALESCE(@Names + ', ', '') + Name, @Names) FROM People

I really liked elegancy of Dana's answer. Just wanted to make it complete.

DECLARE @names VARCHAR(MAX)
SET @names = ''

SELECT @names = @names + ', ' + Name FROM Names 

-- Deleting last two symbols (', ')
SET @sSql = LEFT(@sSql, LEN(@sSql) - 1)
upvote
  flag
If you are deleting the last two symbols ', ', then you need to add ', ' after Name ('SELECT \@names = \@names + Name + ', ' FROM Names'). That way the last two chars will always be ', '. – Justin T
upvote
  flag
In my case I needed to get rid of the leading comma so change the query to SELECT @names = @names + CASE WHEN LEN(@names)=0 THEN '' ELSE ', ' END + Name FROM Names then you don't have to truncate it afterwards. – Tian van Heerden

A ready-to-use solution, with no extra commas:

select substring(
        (select ', '+Name AS 'data()' from Names for xml path(''))
       ,3, 255) as "MyList"

An empty list will result in NULL value. Usually you will insert the list into a table column or program variable: adjust the 255 max length to your need.

(Diwakar and Jens Frandsen provided good answers, but need improvement.)

upvote
  flag
There is a space before the comma when using this :( – slayernoah
1 upvote
  flag
Just replace ', ' with ',' if you don't want the extra space. – Daniel Reis

Oracle 11g Release 2 supports the LISTAGG function. Documentation here.

COLUMN employees FORMAT A50

SELECT deptno, LISTAGG(ename, ',') WITHIN GROUP (ORDER BY ename) AS employees
FROM   emp
GROUP BY deptno;

    DEPTNO EMPLOYEES
---------- --------------------------------------------------
        10 CLARK,KING,MILLER
        20 ADAMS,FORD,JONES,SCOTT,SMITH
        30 ALLEN,BLAKE,JAMES,MARTIN,TURNER,WARD

3 rows selected.

Warning

Be careful implementing this function if there is possibility of the resulting string going over 4000 characters. It will throw an exception. If that's the case then you need to either handle the exception or roll your own function that prevents the joined string from going over 4000 characters.

1 upvote
  flag
For older versions of Oracle, wm_concat is perfect. Its use is explained in the link gift by Alex. Thnks Alex! – toscanelli
upvote
  flag
LISTAGG works perfect! Just read the document linked here. wm_concat removed from version 12c onwards. – asgs

A recursive CTE solution was suggested, but no code provided. The code below is an example of a recursive CTE -- note that although the results match the question, the data doesn't quite match the given description, as I assume that you really want to be doing this on groups of rows, not all rows in the table. Changing it to match all rows in the table is left as an exercise for the reader.

;with basetable as 
(   SELECT id, CAST(name as varchar(max))name, 
        ROW_NUMBER() OVER(Partition By id     order by seq) rw, 
        COUNT(*) OVER (Partition By id) recs 
FROM (VALUES (1, 'Johnny', 1), (1,'M', 2), 
                  (2,'Bill', 1), (2, 'S.', 4), (2, 'Preston', 5), (2, 'Esq.', 6),
        (3, 'Ted', 1), (3,'Theodore', 2), (3,'Logan', 3),
                  (4, 'Peter', 1), (4,'Paul', 2), (4,'Mary', 3)

           )g(id, name, seq)
),
rCTE as (
    SELECT recs, id, name, rw from basetable where rw=1
    UNION ALL
    SELECT b.recs, r.ID, r.name +', '+ b.name name, r.rw+1
    FROM basetable b
         inner join rCTE r
    on b.id = r.id and b.rw = r.rw+1
)
SELECT name FROM rCTE
WHERE recs = rw and ID=4
upvote
  flag
For the flabbergasted: this query inserts 12 rows (a 3 columns) into a temporary basetable, then creates a recursive Common Table Expression (rCTE) and then flattens the name column into a comma-separated string for 4 groups of ids. At first glance, I think this is more work than what most other solutions for SQL Server do. – knb
upvote
  flag
@knb: not sure if that is praise,condemnation,or just surprise. The base table is because I like my examples to actually work, it doesn't really have anything to do with the question. – jmoreno

Postgres arrays are awesome. Example:

Create some test data:

postgres=# \c test
You are now connected to database "test" as user "hgimenez".
test=# create table names (name text);
CREATE TABLE                                      
test=# insert into names (name) values ('Peter'), ('Paul'), ('Mary');                                                          
INSERT 0 3
test=# select * from names;
 name  
-------
 Peter
 Paul
 Mary
(3 rows)

Aggregate them in an array:

test=# select array_agg(name) from names;
 array_agg     
------------------- 
 {Peter,Paul,Mary}
(1 row)

Convert the array to a comma delimited string:

test=# select array_to_string(array_agg(name), ', ') from names;
 array_to_string
-------------------
 Peter, Paul, Mary
(1 row)

DONE

Since PostgreSQL 9.0 it is even easier.

upvote
  flag
If you need more than one column, for example their employee id in brackets use the concat operator: select array_to_string(array_agg(name||'('||id||')' – Richard Fox
upvote
  flag
Not applicable to sql-server, only to mysql – GoldBishop

There are couple more ways in oracle,

    create table name
    (first_name varchar2(30));

    insert into name values ('Peter');
    insert into name values ('Paul');
    insert into name values ('Mary');

    Solution 1:
    select substr(max(sys_connect_by_path (first_name, ',')),2) from (select rownum r, first_name from name ) n start with r=1 connect by prior r+1=r
    o/p=> Peter,Paul,Mary

    Soution 2:
    select  rtrim(xmlagg (xmlelement (e, first_name || ',')).extract ('//text()'), ',') first_name from name
    o/p=> Peter,Paul,Mary

Starting with PostgreSQL 9.0 this is quite simple:

select string_agg(name, ',') 
from names;

In versions before 9.0 array_agg() can be used as shown by hgmnz

upvote
  flag
To do this with columns that are not of type text, you need to add a type cast: SELECT string_agg(non_text_type::text, ',') FROM table – Torben Kohlmeier
upvote
  flag
@TorbenKohlmeier: you only need that for non-character columns (e.g. integer, decimal). It works just fine for varchar or char – a_horse_with_no_name

For Oracle DBs, see this question: How can multiple rows be concatenated into one in Oracle without creating a stored procedure?

The best answer appears to be by @Emmanuel, using the built-in LISTAGG() function, available in Oracle 11g Release 2 and later.

SELECT question_id,
   LISTAGG(element_id, ',') WITHIN GROUP (ORDER BY element_id)
FROM YOUR_TABLE;
GROUP BY question_id

as @user762952 pointed out, and according to Oracle's documentation http://www.oracle-base.com/articles/misc/string-aggregation-techniques.php, the WM_CONCAT() function is also an option. It seems stable, but Oracle explicitly recommends against using it for any application SQL, so use at your own risk.

Other than that, you will have to write your own function; the Oracle document above has a guide on how to do that.

This can be useful too

create table #test (id int,name varchar(10))
--use separate inserts on older versions of SQL Server
insert into #test values (1,'Peter'), (1,'Paul'), (1,'Mary'), (2,'Alex'), (3,'Jack')

DECLARE @t VARCHAR(255)
SELECT @t = ISNULL(@t + ',' + name, name) FROM #test WHERE id = 1
select @t
drop table #test

returns

Peter,Paul,Mary
3 upvote
  flag
Unfortunately this behavior seems not to be officially supported. MSDN says: "If a variable is referenced in a select list, it should be assigned a scalar value or the SELECT statement should only return one row." And there are people who observed problems: sqlmag.com/sql-server/multi-row-variable-assignment-and-orde‌​r – blueling

This method applies to Teradata Aster database only as it utilizes its NPATH function.

Again, we have table Students

SubjectID       StudentName
----------      -------------
1               Mary
1               John
1               Sam
2               Alaina
2               Edward

Then with NPATH it is just single SELECT:

SELECT * FROM npath(
  ON Students
  PARTITION BY SubjectID
  ORDER BY StudentName
  MODE(nonoverlapping)
  PATTERN('A*')
  SYMBOLS(
    'true' as A
  )
  RESULT(
    FIRST(SubjectID of A) as SubjectID,
    ACCUMULATE(StudentName of A) as StudentName
  )
);

Result:

SubjectID       StudentName
----------      -------------
1               [John, Mary, Sam]
2               [Alaina, Edward]

With TABLE type it is extremely easy. Let's imagine that your table is called Students and it has column name.

declare @rowsCount INT
declare @i INT = 1
declare @names varchar(max) = ''

DECLARE @MyTable TABLE
(
  Id int identity,
  Name varchar(500)
)
insert into @MyTable select name from Students
set @rowsCount = (select COUNT(Id) from @MyTable)

while @i < @rowsCount
begin
 set @names = @names + ', ' + (select name from @MyTable where Id = @i)
 set @i = @i + 1
end
select @names

This example is tested in MS SQL Server 2008 R2

To avoid null values you can use CONCAT()

DECLARE @names VARCHAR(500)
SELECT @names = CONCAT(@names, ' ', name) 
FROM Names
select @names
upvote
  flag
It would be nice to know why CONCAT works. A link to MSDN would be nice. – DaveBoltman
   declare @phone varchar(max)='' 
   select @phone=@phone + mobileno +',' from  members
   select @phone
upvote
  flag
Why not +', ' As OP wanted and also you don't delete last ';'. I think this answer is same and also this answer ;). – shA.t
upvote
  flag
I had this problem and I found answer but I want Concatenate with ';' so I paste it here, last element is empty – Hamid Bahmanabady
2 upvote
  flag
When you post your answer here, It should be related to the question And result of your code should be Null, because you start with @phone IS Null and adding to Null will be Null in SQL Server, I think you forgot something like adding = '' after your first line ;). – shA.t
upvote
  flag
No, I post answer after check it and result was not null – Hamid Bahmanabady
upvote
  flag
@shA.t you said correct and I changed it, thanks – Hamid Bahmanabady

This answer will require some privilege in server to work.

Assemblies are a good option for you. There are a lot of sites that explain how to create it. The one I think is very well explained is this one

If you want, I have already created the assembly, and it is possible to download the DLL here.

Once you have downloaded it, you will need to run the following script in your SQL Server:

CREATE Assembly concat_assembly 
   AUTHORIZATION dbo 
   FROM '<PATH TO Concat.dll IN SERVER>' 
   WITH PERMISSION_SET = SAFE; 
GO 

CREATE AGGREGATE dbo.concat ( 

    @Value NVARCHAR(MAX) 
  , @Delimiter NVARCHAR(4000) 

) RETURNS NVARCHAR(MAX) 
EXTERNAL Name concat_assembly.[Concat.Concat]; 
GO  

sp_configure 'clr enabled', 1;
RECONFIGURE

Observe that the path to assembly may be accessible to server. Since you have successfully done all the steps, you can use the function like:

SELECT dbo.Concat(field1, ',')
FROM Table1

Hope it helps!!!

MySQL complete Example:

We have Users which can have many Data's and we want to have an output, where we can see all users Datas in a list:

Result:

___________________________
| id   |  rowList         |
|-------------------------|
| 0    | 6, 9             |
| 1    | 1,2,3,4,5,7,8,1  |
|_________________________|

Table Setup:

CREATE TABLE `Data` (
  `id` int(11) NOT NULL,
  `user_id` int(11) NOT NULL
) ENGINE=InnoDB AUTO_INCREMENT=11 DEFAULT CHARSET=latin1;


INSERT INTO `Data` (`id`, `user_id`) VALUES
(1, 1),
(2, 1),
(3, 1),
(4, 1),
(5, 1),
(6, 0),
(7, 1),
(8, 1),
(9, 0),
(10, 1);


CREATE TABLE `User` (
  `id` int(11) NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=latin1;


INSERT INTO `User` (`id`) VALUES
(0),
(1);

Query:

SELECT User.id, GROUP_CONCAT(Data.id ORDER BY Data.id) AS rowList FROM User LEFT JOIN Data ON User.id = Data.user_id GROUP BY User.id

Use COALESCE - Learn more from here

For an example:

102

103

104

Then write below code in sql server,

Declare @Numbers AS Nvarchar(MAX) -- It must not be MAX if you have few numbers 
SELECT  @Numbers = COALESCE(@Numbers + ',', '') + Number
FROM   TableName where Number IS NOT NULL

SELECT @Numbers

Output would be:

102,103,104
2 upvote
  flag
This is really the best solution IMO as it avoids the encoding issues that FOR XML presents. I used Declare @Numbers AS Nvarchar(MAX) and it worked fine. Can you explain why you recommend not using it please? – EvilDr
1 upvote
  flag
This solution has already been posted 8 years ago! //allinonescript.com/a/194887/986862 – Andre Figueiredo
upvote
  flag
Why is this query returns ??? symbols instead of Cyrillic ones? Is this just output issue? – Akmal Salikhov

With the other answers, the person reading the answer must be aware of a specific domain table such as vehicle or student. The table must be created and populated with data to test a solution.

Below is an example that uses SQL Server "Information_Schema.Columns" table. By using this solution, no tables need to be created or data added. This example creates a comma separated list of column names for all tables in the database.

SELECT
    Table_Name
    ,STUFF((
        SELECT ',' + Column_Name
        FROM INFORMATION_SCHEMA.Columns Columns
        WHERE Tables.Table_Name = Columns.Table_Name
        ORDER BY Column_Name
        FOR XML PATH ('')), 1, 1, ''
    )Columns
FROM INFORMATION_SCHEMA.Columns Tables
GROUP BY TABLE_NAME 
SELECT PageContent = Stuff(
    (   SELECT PageContent
        FROM dbo.InfoGuide
        WHERE CategoryId = @CategoryId
          AND SubCategoryId = @SubCategoryId
        for xml path(''), type
    ).value('.[1]','nvarchar(max)'),
    1, 1, '')
FROM dbo.InfoGuide info

--SQL Server 2005+

CREATE TABLE dbo.Students
(
    StudentId INT
    , Name VARCHAR(50)
    , CONSTRAINT PK_Students PRIMARY KEY (StudentId)
);

CREATE TABLE dbo.Subjects
(
    SubjectId INT
    , Name VARCHAR(50)
    , CONSTRAINT PK_Subjects PRIMARY KEY (SubjectId)
);

CREATE TABLE dbo.Schedules
(
    StudentId INT
    , SubjectId INT
    , CONSTRAINT PK__Schedule PRIMARY KEY (StudentId, SubjectId)
    , CONSTRAINT FK_Schedule_Students FOREIGN KEY (StudentId) REFERENCES dbo.Students (StudentId)
    , CONSTRAINT FK_Schedule_Subjects FOREIGN KEY (SubjectId) REFERENCES dbo.Subjects (SubjectId)
);

INSERT dbo.Students (StudentId, Name) VALUES
    (1, 'Mary')
    , (2, 'John')
    , (3, 'Sam')
    , (4, 'Alaina')
    , (5, 'Edward')
;

INSERT dbo.Subjects (SubjectId, Name) VALUES
    (1, 'Physics')
    , (2, 'Geography')
    , (3, 'French')
    , (4, 'Gymnastics')
;

INSERT dbo.Schedules (StudentId, SubjectId) VALUES
    (1, 1)      --Mary, Physics
    , (2, 1)    --John, Physics
    , (3, 1)    --Sam, Physics
    , (4, 2)    --Alaina, Geography
    , (5, 2)    --Edward, Geography
;

SELECT 
    sub.SubjectId
    , sub.Name AS [SubjectName]
    , ISNULL( x.Students, '') AS Students
FROM
    dbo.Subjects sub
    OUTER APPLY
    (
        SELECT 
            CASE ROW_NUMBER() OVER (ORDER BY stu.Name) WHEN 1 THEN '' ELSE ', ' END
            + stu.Name
        FROM
            dbo.Students stu
            INNER JOIN dbo.Schedules sch
                ON stu.StudentId = sch.StudentId
        WHERE
            sch.SubjectId = sub.SubjectId
        ORDER BY
            stu.Name
        FOR XML PATH('')
    ) x (Students)
;

Not that I have done any analysis on performance as my list had less than 10 items but I was amazed after looking thru the 30 odd answers I still had a twist on a similar answer already given similar to using COALESCE for a single group list and didn't even have to set my variable (defaults to NULL anyhow) and it assumes all entries in my source data table are non blank:

DECLARE @MyList VARCHAR(1000), @Delimiter CHAR(2) = ', '
SELECT @MyList = CASE WHEN @MyList > '' THEN @MyList + @Delimiter ELSE '' END + FieldToConcatenate FROM MyData

I am sure COALESCE internally uses the same idea. Lets hope MS don't change this on me.

You need to create a variable that will hold your final result and select into it, like so.

Easiest Solution

DECLARE @char VARCHAR(MAX);

SELECT @char = COALESCE(@char + ', ' + [column], [column]) 
FROM [table];

PRINT @char;

In SQL Server vNext this will be built in with the STRING_AGG function, read more about it here: https://msdn.microsoft.com/en-us/library/mt790580.aspx

SQL Server 2017 and SQL Azure: STRING_AGG

Starting with the next version of SQL Server, we can finally concatenate across rows without having to resort to any variable or XML witchery.

Without grouping

SELECT STRING_AGG(Name, ', ') AS Departments
FROM HumanResources.Department;

With grouping :

SELECT GroupName, STRING_AGG(Name, ', ') AS Departments
FROM HumanResources.Department
GROUP BY GroupName;

With grouping and sub-sorting

SELECT GroupName, STRING_AGG(Name, ', ') WITHIN GROUP (ORDER BY Name ASC) AS Departments
FROM HumanResources.Department 
GROUP BY GroupName;
1 upvote
  flag
And, unlike CLR solutions, you have control over the sorting. – canon
upvote
  flag
This works with SQL Azure. Great answer! – user2721607
upvote
  flag
This also worked for me in Azure SQL. Brilliant! – Kevin Stone

Although it's too late, and already has many solutions. Here is simple solution for MySQL:

SELECT t1.id,
        GROUP_CONCAT(t1.id) ids
 FROM table t1 JOIN table t2 ON (t1.id = t2.id)
 GROUP BY t1.id

Not the answer you're looking for? Browse other questions tagged or ask your own question.