sql语句优化问题,现在这个sql 运行速度比较慢,怎么优化一下? 谢谢!

[littleboys]

Select count(*) FROM T_CL_CUST
WHERE EXISTS
(SELECT * FROM T_BILL_PLAN
WHERE T_CL_CUST.CALL_LIST_ID = T_BILL_PLAN.CALL_LIST_ID AND EXISTS
(SELECT * FROM V_BILL_PLAN WHERE TASK_ID = 0000040142 AND T_BILL_PLAN.PLAN_SEQ = V_BILL_PLAN.PLAN_SEQ));

[sijian2001]

你套用了两个EXISTS，当然慢啦。你用下面的这个试一试。
SELECT COUNT(*)
FROM
(SELECT UNIQUE T1.PK --(Primary Key)
FROM T_CL_CUST T1,T_BILL_PLAN T2,V_BILL_PLAN T3
WHERE T1.CALL_LIST_ID = T2.CALL_LIST_ID AND T3.TASK_ID = 0000040142 AND T2.PLAN_SEQ = T3.PLAN_SEQ)

[马前小卒]

up

[vision2000]

up

[littleboys]

好的,我试试

[littleboys]

性能有很大的改善

[Croatia]

内联结，应该比你的exists快，
还有，你可以把你的对各个表的限制，放到各个表里面去，看看执行效果呢。

SELECT COUNT(*)
FROM
(SELECT UNIQUE T1.PK --(Primary Key)
FROM T_CL_CUST T1,T_BILL_PLAN T2,
(select * from V_BILL_PLAN where TASK_ID = 0000040142 ) T3
WHERE T1.CALL_LIST_ID = T2.CALL_LIST_ID AND T2.PLAN_SEQ = T3.PLAN_SEQ)

[David1289]

用Exists,in ,distinct 等都是比较耗资源地方式，能不用最好不用。