How to create a SQL Server function to “join” multiple rows from a subquery into a single delimited field? [duplicate]

Answer 1

In SQL Server 2005

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

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In SQL Server 2016

you can use the FOR JSON syntax

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

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And in SQL Server 2017, Azure SQL Database

You can use the new STRING_AGG function