Har T-SQL en aggregeret funktion til at sammenkæde strenge?

til SQL Server 2017 og nyere brug:

STRING_AGG()

set nocount on;
declare @YourTable table (RowID int, HeaderValue int, ChildValue varchar(5))
insert into @YourTable VALUES (1,1,'CCC')
insert into @YourTable VALUES (2,2,'B<&>B')
insert into @YourTable VALUES (3,2,'AAA')
insert into @YourTable VALUES (4,3,'<br>')
insert into @YourTable VALUES (5,3,'A & Z')
set nocount off
SELECT
    t1.HeaderValue
        ,STUFF(
                   (SELECT
                        ', ' + t2.ChildValue
                        FROM @YourTable t2
                        WHERE t1.HeaderValue=t2.HeaderValue
                        ORDER BY t2.ChildValue
                        FOR XML PATH(''), TYPE
                   ).value('.','varchar(max)')
                   ,1,2, ''
              ) AS ChildValues
    FROM @YourTable t1
    GROUP BY t1.HeaderValue

SELECT
    HeaderValue, STRING_AGG(ChildValue,', ')
    FROM @YourTable
    GROUP BY HeaderValue

OUTPUT:

HeaderValue 
----------- -------------
1           CCC
2           B<&>B, AAA
3           <br>, A & Z

(3 rows affected)

til SQL Server 2005 og op til 2016 skal du gøre noget som dette:

--Concatenation with FOR XML and eleminating control/encoded character expansion "& < >"
set nocount on;
declare @YourTable table (RowID int, HeaderValue int, ChildValue varchar(5))
insert into @YourTable VALUES (1,1,'CCC')
insert into @YourTable VALUES (2,2,'B<&>B')
insert into @YourTable VALUES (3,2,'AAA')
insert into @YourTable VALUES (4,3,'<br>')
insert into @YourTable VALUES (5,3,'A & Z')
set nocount off
SELECT
    t1.HeaderValue
        ,STUFF(
                   (SELECT
                        ', ' + t2.ChildValue
                        FROM @YourTable t2
                        WHERE t1.HeaderValue=t2.HeaderValue
                        ORDER BY t2.ChildValue
                        FOR XML PATH(''), TYPE
                   ).value('.','varchar(max)')
                   ,1,2, ''
              ) AS ChildValues
    FROM @YourTable t1
    GROUP BY t1.HeaderValue

OUTPUT:

HeaderValue ChildValues
----------- -------------------
1           CCC
2           AAA, B<&>B
3           <br>, A & Z

(3 row(s) affected)

Pas også på, ikke alle FOR XML PATH sammenkædninger vil korrekt håndtere XML-specialtegn som mit eksempel ovenfor vil.