How to create a SQL Server function to join multiple rows from a subquery into a single delimited field?
If you're using SQL Server 2005, you could use the FOR XML PATH command.
SELECT [VehicleID]
, [Name]
, (STUFF((SELECT CAST(', ' + [City] AS VARCHAR(MAX))
FROM [Location]
WHERE (VehicleID = Vehicle.VehicleID)
FOR XML PATH ('')), 1, 2, '')) AS Locations
FROM [Vehicle]
It's a lot easier than using a cursor, and seems to work fairly well.
Update
For anyone still using this method with newer versions of SQL Server, there is another way of doing it which is a bit easier and more performant using theSTRING_AGG
method that has been available since SQL Server 2017.
SELECT [VehicleID]
,[Name]
,(SELECT STRING_AGG([City], ', ')
FROM [Location]
WHERE VehicleID = V.VehicleID) AS Locations
FROM [Vehicle] V
This also allows a different separator to be specified as the second parameter, providing a little more flexibility over the former method.
How to concatenate text from multiple rows into a single text string in SQL Server
If you are on SQL Server 2017 or Azure, see Mathieu Renda answer.
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 (''), TYPE
).value('text()[1]','nvarchar(max)') [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 (''), TYPE
).value('text()[1]','nvarchar(max)'), 2, 1000) [Students]
FROM dbo.Students ST2
Combine multiple results in a subquery into a single comma-separated value
1. Create the UDF:
CREATE FUNCTION CombineValues
(
@FK_ID INT -- The foreign key from TableA which is used
-- to fetch corresponding records
)
RETURNS VARCHAR(8000)
AS
BEGIN
DECLARE @SomeColumnList VARCHAR(8000);
SELECT @SomeColumnList =
COALESCE(@SomeColumnList + ', ', '') + CAST(SomeColumn AS varchar(20))
FROM TableB C
WHERE C.FK_ID = @FK_ID;
RETURN
(
SELECT @SomeColumnList
)
END
2. Use in subquery:
SELECT ID, Name, dbo.CombineValues(FK_ID) FROM TableA
3. If you are using stored procedure you can do like this:
CREATE PROCEDURE GetCombinedValues
@FK_ID int
As
BEGIN
DECLARE @SomeColumnList VARCHAR(800)
SELECT @SomeColumnList =
COALESCE(@SomeColumnList + ', ', '') + CAST(SomeColumn AS varchar(20))
FROM TableB
WHERE FK_ID = @FK_ID
Select *, @SomeColumnList as SelectedIds
FROM
TableA
WHERE
FK_ID = @FK_ID
END
Multiple rows to one comma-separated value in Sql Server
Test Data
DECLARE @Table1 TABLE(ID INT, Value INT)
INSERT INTO @Table1 VALUES (1,100),(1,200),(1,300),(1,400)
Query
SELECT ID
,STUFF((SELECT ', ' + CAST(Value AS VARCHAR(10)) [text()]
FROM @Table1
WHERE ID = t.ID
FOR XML PATH(''), TYPE)
.value('.','NVARCHAR(MAX)'),1,2,' ') List_Output
FROM @Table1 t
GROUP BY ID
Result Set
╔════╦═════════════════════╗
║ ID ║ List_Output ║
╠════╬═════════════════════╣
║ 1 ║ 100, 200, 300, 400 ║
╚════╩═════════════════════╝
SQL Server 2017 and Later Versions
If you are working on SQL Server 2017 or later versions, you can use built-in SQL Server Function STRING_AGG to create the comma delimited list:
DECLARE @Table1 TABLE(ID INT, Value INT);
INSERT INTO @Table1 VALUES (1,100),(1,200),(1,300),(1,400);
SELECT ID , STRING_AGG([Value], ', ') AS List_Output
FROM @Table1
GROUP BY ID;
Result Set
╔════╦═════════════════════╗
║ ID ║ List_Output ║
╠════╬═════════════════════╣
║ 1 ║ 100, 200, 300, 400 ║
╚════╩═════════════════════╝
How do I concatenate strings from a subquery into a single row in mysql?
by using the GROUP_CONCAT() function and a GROUP BY call. here's an example query
SELECT
p.package_id,
p.package_name,
p.price,
GROUP_CONCAT(pz.zone_id SEPARATOR ',') as zone_list
FROM
package p
LEFT JOIN package_zone pz ON p.package_id = pz.package_id
GROUP BY
p.package_id
you should still be able to order by zone_id s (or zone_list), and instead of using LIKE
, you can use WHERE zp.zone_id = 'Z1'
or something similar.
grouping based on name
You can use XML stuff combination
select distinct c1,
STUFF((Select ','+c2
from table1 T1
where T1.c1 =T2.c1
FOR XML PATH('')),1,1,'') from table1 T2
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