Question

I am new to SQL and struggling with very slow view, it should return newest event for specific person. This view doesnt use PERSON entity (but it could). The relation Person->Event is oneToMany.

Structure

 
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Below is very slow view, which works too slow (indexes on PERSON_ID and ID are created but it is still very slow)

PERSON: ID NAME EVENT: PERSON_ID EVENT_DESC EVENT_TYPE IDX

View to be changed (too slow)

select * from V_CURRENT_EVENT_FOR_PERSON where person_id = 123456

I tried to change it to:

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
      )
    ))

But here 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 never retures any results because of the select * from V_CURRENT_EVENT_FOR_PERSON where person_id = 123456

Answer 1

If I understood your question correctly, the following should do what you want:

.popover("show")

SQL - view very slow or doesnt return any results

1 个答案: