pl/sql可以得出结果，sqlplus会报不存在的lob值。

select a.CI_ID,to_char(

(select wm_concat(decode(instr(a.stu_ids,b.stu_id),0,null,b.stu_name))

  from pm_stu b

  )

) STU_NAME 

from pm_ci a where a.ci_id is not null;