数据库中逗号隔开的值去除重复项

需求

将'1,1,2,3,4,4,4' 转换为'1,2,3,4'

语句

DECLARE @Test varchar(100)='1,1,2,3,4,4,4'
SELECT
STUFF
(
    (
        SELECT DISTINCT ','+ y.sCode FROM
        (
            SELECT sCodes = CONVERT(xml,'<root><v>' + REPLACE(@Test, ',', '</v><v>') + '</v></root>')
        ) x
        OUTER APPLY
        (
            SELECT sCode = N.v.value('.', 'varchar(100)') FROM x.sCodes.nodes('/root/v') N(v)
        )y
        FOR XML PATH('')
    )
    ,1,1,''
) as sCodes