sql server函数

ALTER FUNCTION f_refresh_comDept(@fileid int)
returns nvarchar(1024)
as
BEGIN
    declare @returns nvarchar(1024)
    select  @returns= isnull(@returns+',','')+b.departmentName
    from config_department_file a
    join config_department b
    on a.departmentID=b.departmentID
    where a.fileid=@fileid
  
    return @returns
end