What is the equivalent of String.Join on TSQL? [duplicate]

Answer 1

SELECT CAST(TextColumn + ';' AS VARCHAR(MAX)) 
FROM SomeTable
WHERE SomeOtherColumn = 'Y'
FOR XML PATH ('')

If you don't like the trailing ; you can remove the character from the result.

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EDIT IN 2017

Many platforms now support the windowing function LISTAGG()

Answer 2

This should do the trick:

DECLARE @Result VARCHAR(MAX);

SELECT
    @Result = CASE
        WHEN @Result IS NULL
        THEN T.TextColumn
        ELSE @Result + ';' + T.TextColumn
    END
FROM
    SomeTable AS T
WHERE
    T.SomeOtherColumn = 'Y';

SELECT @Result