Oracle選擇帶子查詢

Question

我有兩個甲骨文選擇查詢

SELECT loc.location AS LOCATION , req.requisition AS REQ 
FROM location_view loc, requisition_view req, association ass 
WHERE loc.name = 'ABC' AND req.name = 'TRANSFER' 
AND ass.entity_id_2 = req.entity_id AND ass.entity_id_1 = loc.entity_id

結果看起來像：

其他查詢如下：

 SELECT req.requisition AS req, exp.experiment AS expt 
 FROM experiment_view exp, requisition_view req, association_view ass 
 WHERE expt.name = 'RETRIEVAL'AND req.name = 'TRANSFER' 
 AND ass.entity_id_2 = req.entity_id AND ass.entity_id_1 = expt.entity_id 

結果 ：

我試圖結合這兩個SELECT查詢，以便我看到這些結果：

我應該使用子查詢來查看組合結果還是有其他優化方法？

Answer 1

我不確定所提供的解決方案是否正確。 他們都使用1連接到關聯表。 您需要2。因為關聯看上去是一個通用的映射表，所以將位置鏈接到申請的行與將請求鏈接到實驗的行不同。 也許我錯了，但我會去：

SELECT
  loc.location as LOCATION , 
  req.requisition as REQ, 
  exp.experiment as EXPT
FROM  location_view    loc
JOIN  association      asslr ON asslr.entity_id_1 = loc.entity_id
JOIN  requisition_view req   ON asslr.entity_id_2 = req.entity_id and req.name = 'TRANSFER'
JOIN  association_view assre ON assre.entity_id_2 = req.entity_id
JOIN  experiment_view  exp   ON assre.entity_id_1 = exp.entity_id AND exp.name = 'RETRIEVAL'
WHERE loc.name = 'ABC' 

Answer 2

這兩個查詢幾乎相同。 結果可以在一個公共元素上連接在一起，因此，可以將它們編寫為一個查詢：

select loc.location as LOCATION , req.requisition as REQ, exp.experiment as expt
from location_view loc, requisition_view req, association ass, experiment_view exp
where  loc.name = 'ABC' and req.name = 'TRANSFER' and ass.entity_id_2 = req.entity_id and ass.entity_id_1 = loc.entity_id and ass.entity_id_1 = expt.entity_id and expt.name = 'RETRIEVAL'

不過，這是一種古老的非標准方式來編寫查詢； 研究INNER JOIN關鍵字的工作方式； 這是我如何安排此查詢的方式：

select
  loc.location as LOCATION , 
  req.requisition as REQ, 
  exp.experiment as expt
from 
  association ass
  INNER JOIN
  location_view loc
  ON
    ass.entity_id_1 = loc.entity_id

  INNER JOIN 
  requisition_view req 
  on 
    ass.entity_id_2 = req.entity_id

  INNER JOIN
  experiment_view expt
  ON
    ass.entity_id_1 = expt.entity_id

WHERE        
  loc.name = 'ABC' and
  req.name = 'TRANSFER' and
  expt.name = 'RETRIEVAL'

Answer 3

SELECT loc.location AS location, 
       req.requisition AS req,
       exp.experiment AS expt
  FROM location_view loc
 INNER JOIN association ass
    ON loc.entity_id = ass.entity_id_1
 INNER JOIN requisition_view req
    ON req.entity_id = ass.entity_id_2
 INNER JOIN experiment_view exp
    ON expt.entity_id = ass.entity_id_1
 WHERE loc.name = 'ABC'
   AND req.name = 'TRANSFER' 
   AND expt.name = 'RETRIEVAL'