oracle--联表update不允许使用order by

update bpm_biz b set dealer_memo = (select e.ASSIGN_MEMO  from BPM_TASK t ,BPM_TASK_EXT e where t.TASK_ID = e.TASK_ID and b.INST_ID = t.INST_D and rownum=1  and t.PRE_TASKNAME = 'XXXXX'  and t.TASK_NAME = 'XXXXX'   order by t.ASSIGN_TIME desc )where exists (select 1  from BPM_TASK t ,BPM_TASK_EXT e where t.TASK_ID = e.TASK_ID and b.INST_ID = t.INST_D and rownum=1  and t.PRE_TASKNAME = 'XXXXX'  and t.TASK_NAME = 'XXXXX'   order by t.ASSIGN_TIME desc )

 

 

原因：这种语句测试时会报“缺少右括号”

 

解决方案：order by 尽量用 group by 代替，尽管性能慢一些