WITH Data AS (
    SELECT 1 UserId, 'A' Code 
    UNION ALL 
    SELECT 1, 'C5'
    UNION ALL 
    SELECT 1, 'X'
    UNION ALL 
    SELECT 2, 'V3'
    UNION ALL 
    SELECT 3, 'B'
    UNION ALL 
    SELECT 3, 'D'
    UNION ALL 
    SELECT 3, NULL
    UNION ALL 
    SELECT 3, 'F4'
    UNION ALL 
    SELECT 4, NULL
)
SELECT U.UserId, STUFF((
    SELECT ','+Code FROM Data WHERE Data.UserID = U.UserID FOR XML PATH('')
), 1, 1, '') Code 
FROM (SELECT DISTINCT UserID FROM Data) U

只需将 Data CTE 替换为您的表名即可.

Just replace the Data CTE with your table name and you're done.