带有多个 LEFT JOINS 和 VIEWS 的 SUM

Question

我需要对两个不同表（prognosis_scores 和 question_scores）中的两列（pts_won）求和，但它不能正常工作。 如果有很多progression_scores 或很多question_scores，则总和将不准确（例如，如果有一个question_scores 和三个progression_scores，则总和将加上您question_scores 的pts_won 的3 倍）：

这里总和的结果是 30，我希望它是 10

| prognosis_scores | question_scores|
| ---------------- | -------------- |
| pts_won          | pts_won        |

这是我的代码

    CREATE VIEW score_calculations
    AS SELECT 
    users.id as user_id,
    users.name as name,
    users.company_id as company_id,
    users.team_id as team_id,
    users.email_verified as email_verified,
    -- users.email as email,
    SUM(COALESCE(prognosis_scores."pts_won", 0) + COALESCE (question_scores."pts_won", 0) ) as pts_won,
    SUM(prognosis_scores."good_gap") as good_gap,
    SUM(prognosis_scores."good_score") as good_score,
    SUM(prognosis_scores."isGoodPrognosis"::INT) as good_winner
    FROM users
    
    LEFT JOIN prognosis_scores
    ON prognosis_scores.user_id=users.id
    LEFT JOIN question_scores
    ON question_scores.user_id=users.id
    GROUP BY users.id , users.name, users.company_id,team_id,email_verified;

我怎样才能通过一次将两者相加来解决这个问题？

Answer 1

在 Postgres 中，这可能是最简单的横向连接：

SELECT u.id as user_id, u.name, u.company_id, u.team_id, u.email_verified,
-- users.email as email,
   COALESCE(ps.pts_won, 0) + COALESCE (qs.pts_won, 0) ) as pts_won,
   ps.good_gap, ps.good_score, ps.good_winner
FROM users u LEFT JOIN LATERAL
     (SELECT SUM(ps."pts_won") as pts_won,
             SUM(ps.good_gap) as good_gap,
             SUM(ps.good_score) as good_score,
             SUM(ps."isGoodPrognosis"::INT) as good_winner
      FROM prognosis_scores ps
      WHERE ps.user_id = u.id
     ) ps
     ON 1=1 LEFT JOIN LATERAL
     (SELECT SUM(qs."pts_won") as pts_won
      FROM question_scores qs
      WHERE qs.user_id = u.id
     ) qs
     ON 1=1;

这可以让您在执行JOIN 之前进行汇总 -- 所以总数是准确的。

注意事项：

• 表别名使查询更易于编写和阅读。
• 默认列别​​名是列名，所以不用写u.name as name。我想，如果你喜欢打字也没什么坏处。
• 避免在列上使用双引号。如果表格是这样定义的，你会被卡住——所以你应该修正这个定义。