Question

我的代码中有这个SQL，并且子查询的重复使我担心这不是有效写入的。

我的数据库有一个features，responses和participants的表格。参与者为每个特征给出评级（D，P，B，I，R，Q之一）。

SELECT f.id, f.name,
(SELECT COUNT(r.id) FROM responses r LEFT JOIN participants p ON r.id_participant = p.id WHERE p.is_ignored IS NULL AND r.is_deleted IS NULL AND r.id_feature = f.id AND p.category LIKE :p_category) AS nr_r, 
(SELECT SUM(r.is_D) FROM responses r LEFT JOIN participants p ON r.id_participant = p.id WHERE p.is_ignored IS NULL AND r.is_deleted IS NULL AND r.id_feature = f.id AND p.category LIKE :p_category) AS is_D, 
(SELECT SUM(r.is_P) FROM responses r LEFT JOIN participants p ON r.id_participant = p.id WHERE p.is_ignored IS NULL AND r.is_deleted IS NULL AND r.id_feature = f.id AND p.category LIKE :p_category) AS is_P, 
(SELECT SUM(r.is_B) FROM responses r LEFT JOIN participants p ON r.id_participant = p.id WHERE p.is_ignored IS NULL AND r.is_deleted IS NULL AND r.id_feature = f.id AND p.category LIKE :p_category) AS is_B, 
(SELECT SUM(r.is_I) FROM responses r LEFT JOIN participants p ON r.id_participant = p.id WHERE p.is_ignored IS NULL AND r.is_deleted IS NULL AND r.id_feature = f.id AND p.category LIKE :p_category) AS is_I, 
(SELECT SUM(r.is_R) FROM responses r LEFT JOIN participants p ON r.id_participant = p.id WHERE p.is_ignored IS NULL AND r.is_deleted IS NULL AND r.id_feature = f.id AND p.category LIKE :p_category) AS is_R, 
(SELECT SUM(r.is_Q) FROM responses r LEFT JOIN participants p ON r.id_participant = p.id WHERE p.is_ignored IS NULL AND r.is_deleted IS NULL AND r.id_feature = f.id AND p.category LIKE :p_category) AS is_Q,
(SELECT (is_D + is_P)/(is_D + is_P + is_B + is_I)) as yay,
(SELECT (is_P + is_B)/(is_D + is_P + is_B + is_I)) as boo
FROM features f 
WHERE f.is_deleted IS NULL AND f.id_survey=:id_project
ORDER BY f.id ASC;

该查询的输出是一个总计表，类似于

577 App registration    989   36   21   38  201  42   6  0.1926  0.1993
578 Login PIN           989  279  118  137  394  41  20  0.4278  0.2748
579 Manage all services 989  287  207  127  331  23  14  0.5189  0.3508
580 Rewards             989  344  157   64  386  19  19  0.5268  0.2324
581 Offers              989  226   93   37  542  72  19  0.3552  0.1448

查询目前需要4.4387秒来运行具有989个参与者的数据集，14个特征（因此有13,846个个体评级）。很确定这很臭。

是否有更有效的方式来编写该查询？

这是GROUP BY有用的东西吗？

Answer 1

如果我理解你的查询，你在每个子查询中都有相同的谓词，然后你可以轻松地用连接替换所有子选择并执行分组。聚合物（yay和boo）的计算在外层计算：

SELECT id, name, nr_r, is_D, ...
     , (is_D + is_P)/(is_D + is_P + is_B + is_I) yay
     , (is_P + is_B)/(is_D + is_P + is_B + is_I) boo
FROM (
     SELECT f.id, f.name
         , count(r.id) AS nr_r
         , sum(r.is_D) as is_D
         , ...
     FROM features f
     LEFT JOIN responses r 
         ON r.id_feature = f.id
        AND r.is_deleted IS NULL 
     LEFT JOIN participants p 
         ON r.id_participant = p.id
        AND p.is_ignored IS NULL
        AND p.category LIKE :p_category  
     WHERE f.is_deleted IS NULL 
       AND f.id_survey=:id_project
     GROUP BY f.id, f.name
) AS T
ORDER BY ...

更有效的SQL消除多个子查询？

1 个答案: