Oracle SQL查詢性能

Question

我有3個表交易者，city_state，city_present。

我在交易員表中有400萬行，我的查詢至少需要20秒。 city_present和cities表中幾乎沒有記錄。

以下是我的查詢。

 
    
 

select t.trader_id, t.name, t.city, t.state from 
    (
    SELECT distinct c.city, c.state 
    FROM city_present p,city_state c 
    WHERE p.name = 'TEST_TEST' 
    AND c.city = p.city 
    AND c.state = p.state 
    ) 
    cs, trader t 
    where 
    AND t.city = cs.city 
    AND t.state = cs.state 
    AND t.name = 'john test' 
    AND t.is_valid= 1 

我對客戶（市，州，名稱，valid_customer）指數 子查詢所需的時間比第二個是20秒左右服用..它是外部查詢較少。

有人可以幫助我如何減少查詢時間。

Answer 1

我假設你有一個trader.name的索引，可能還包括trader.is_valid？

而且是真正需要的區別嗎？這是否真的需要成爲一個內聯視圖，還是可以成爲一個常規聯接？

Answer 2

有一些事情你可以嘗試不添加任何東西到您的模式：在你的子查詢，你永遠不會選擇city_present什麼，所以你可以把它變成IN/EXISTS

select t.trader_id, t.name, t.city, t.state from 
(
SELECT c.city, c.state 
FROM city_state c 
WHERE EXISTS (
    select null 
    from city_present p 
    where 
    p.name = 'TEST_TEST' 
    AND c.city = p.city 
    AND c.state = p.state) 
) 
cs, trader t 
where 
AND t.city = cs.city 
AND t.state = cs.state 
AND t.name = 'john test' 
AND t.is_valid= 1 

然後，同樣的道理也適用到CS。所以，你可以改寫爲：

select t.trader_id, t.name, t.city, t.state from 
trader t 
where 
exists (
    SELECT null 
    FROM city_state c 
    WHERE EXISTS (
     select null 
     from city_present p 
     where 
     p.name = 'TEST_TEST' 
     AND c.city = p.city 
     AND c.state = p.state) 
    AND t.city = c.city 
    AND t.state = c.state 
) 
AND t.name = 'john test' 
AND t.is_valid= 1 

您也可以嘗試壓扁的子查詢：

select t.trader_id, t.name, t.city, t.state from 
trader t 
where 
exists (
    SELECT null 
    FROM city_present p,city_state c 
    WHERE p.name = 'TEST_TEST' 
    AND c.city = p.city 
    AND c.state = p.state 
    AND t.city = c.city 
    AND t.state = c.state 
) 
AND t.name = 'john test' 
AND t.is_valid= 1 

從這裏，你應該調查關於索引：

• trader.name和/或交易.id
• （city_state.city，city_state.state）and（city_present.city，city_present.state）