需要在SQL語句

Question

不能優化我有一個SQL查詢：

select person from table t1 
inner join person_history ph 
on t1.person = ph.person 
and t1.person not in (select person from person_history 
         where effective_date < '01-01-2013') 
and ph.person.effective_date > '01-01-2013' 

因爲person_history含有大量的記錄，此查詢的時間過長。

如何優化此代碼？

Answer 1

你就不能這樣做：

select person from table t1 
inner join person_history ph 
on t1.person = ph.person 
where ph.effective_date >= '01-01-2013' 

Answer 2

你不必排除NOT IN，因爲它已經被排除在WHERE過濾器！ 的SQL將是簡單如下：

select person from table t1 
inner join person_history ph on t1.person=ph.person 
where effective_date > '01-01-2013' 

或者：

select person from table t1 
WHERE person IN(select ph.person from person_history ph 
where effective_date > '01-01-2013' and t1.person=ph.person)