WITH test (id, zhi)
 AS ( 
 SELECT 'a', 1
 UNION ALL 
 SELECT 'a', 2
 UNION ALL 
 SELECT 'a', 2
 UNION ALL 
 SELECT 'b', 1
 UNION ALL 
 SELECT 'b', 3)
 
 select a.id,
 stuff((select ','+CONVERT(VARCHAR(5),zhi) from test b 
        where b.id=a.id 
        for xml path('')),1,1,'') 'zhi'
 from test a
 group by  a.id
 
 /*
 id   zhi
 ---- ----------------------------------------------------------------------------------------------------------------
 a    1,2,2
 b    1,3
 
 (2 行受影响)
 
 
 */