识别正在使用哪个外键ORACLE SQL

Question

我有两个表，我想获取quality_score_A和Quality_score_B的平均quality_score。

这是我尝试过的方法，但这使我在quality_score_a和quality_score_b中具有相同的值

SELECT AVG (quality_score),AVG (quality_score)
FROM REVIEW
JOIN Score_table on score.quality_score_A
JOIN Score_table on score.quality_score_B
WHERE PRODUCT_ID  = 2
GROUP BY PRODUCT_ID;

请参阅附件表的布局和所需的结果

Answer 1

您需要指定要加入的条件：

SELECT   product_id, AVG(a.quality_score), AVG(b.quality_score)
FROM     review r
JOIN     score_table a ON r.quality_score_a = a.score_id
JOIN     score_table b ON r.quality_score_a = b.score_id
WHERE    product_id = 2
GROUP BY product_id

Answer 2

我认为最简单的方法是取消结果：

select r.product_id,
       avg(case when which = 'a' then s.quality_score end) as a_avg,
       avg(case when which = 'b' then s.quality_score end) as b_avg
from ((select r.product_id, quality_score_a as score_id, 'a' as which
       from reviews r
      ) union all
      (select r.product_id, quality_score_b as score_id, 'b' as which
       from reviews r
      )
     ) r join
     scores s
     on r.score_id = s.score_id
group by r.product_id