SQL - 查看速度很慢或不返回任何結果

我是SQL新手，並且遇到非常慢的視圖，應該爲特定的人員返回最新的事件。這個視圖並不使用PERSON實體（但它可以）。關係Person-> Event是oneToMany。SQL - 查看速度很慢或不返回任何結果

結構

PERSON: 
ID 
NAME 

EVENT: 
PERSON_ID 
EVENT_DESC 
EVENT_TYPE 
IDX

下面是很慢的觀點，其工作速度太慢（上PERSON_ID和ID索引創建的，但它仍然是非常慢）

select * from V_CURRENT_EVENT_FOR_PERSON where person_id = 123456

查看（太慢）

create or replace force view "V_CURRENT_EVENT_FOR_PERSON" ("PERSON_ID", 
    "EVENT_DESC", "EVENT_TYPE") as 
select * from (SELECT EVENT.PERSON_ID   AS PERSON_ID, 

    EVENT.EVENT_DESC AS EVENT_DESC, 
    EVENT.EVENT_TYPE  AS EVENT_TYPE 

    FROM PERSON_EVENT_DATA EVENT 
    WHERE EVENT.ID = 
    (SELECT EVENT2.ID 
    FROM PERSON_EVENT_DATA EVENT2 
    WHERE EVENT2.PERSON_ID = EVENT.PERSON_ID 
    GROUP BY EVENT2.PERSON_ID, 
     EVENT2.IDX, 
     EVENT2.ID 
    HAVING EVENT2.IDX = 
     (SELECT MAX(EVENT3.IDX) 
     FROM PERSON_EVENT_DATA EVENT3 
     WHERE EVENT3.PERSON_ID = EVENT2.PERSON_ID 
    ) 
    ))

我試圖將其更改爲：

create or replace force view "V_CURRENT_EVENT_FOR_PERSON" ("PERSON_ID", 
    "EVENT_DESC", "EVENT_TYPE") as 
select * from (SELECT EVENT.PERSON_ID   AS PERSON_ID, 

    EVENT.EVENT_DESC AS EVENT_DESC, 
    EVENT.EVENT_TYPE  AS EVENT_TYPE 

    FROM PERSON_EVENT_DATA EVENT order by EVENT.idx desc 

) where rownum = 1

但這裏select * from V_CURRENT_EVENT_FOR_PERSON where person_id = 123456從未retures因爲rownum = 1

來源

2016-02-12 michealAtmi

任何結果。如果我理解正確你的問題，下面應該做你想要什麼：

select person_id, event_desc, event_type 
from (
    select person_id, 
     event_desc, 
     event_type, 
     row_number() over (partition by person_id order by idx desc) as rn 
    from person_event_data 
) t 
where rn = 1;

來源

2016-02-12 20:50:04

工作速度提高一倍，謝謝。我將它包裝在VIEW中。它在實踐中如何運作？當我選擇* from V_CURRENT_EVENT_FOR_PERSON where person_id = 123456 ...它會搜索所有人的所有事件，然後爲person_id應用條件，或者它只搜索人員123456的事件？ – michealAtmi

@michealAtmi：檢查執行計劃。我會假設Oracle將'where person_id ='的條件推入視圖中，並且不對所有行進行評估。但是隻有執行計劃才能告訴你。 –

新問題發生：當我做分頁（每頁10個元素，關於page2的qyery）查詢如下：select p。* from person p left outer join V_CURRENT_EVENT_FOR_PERSON vv on p.id = vv.person_id where rownum> 10，then nothing返回.. – michealAtmi

SQL - 查看速度很慢或不返回任何結果

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