有没有一种方法可以在SQL中根据一个ID替换结果顺序，同时又根据另一个ID保持分组？

问题描述

我在Postgresql中有此查询：

(SELECT q.question,q.category_id,a.id,a.question_id,a.answer
    FROM questions q,answers a
    WHERE q.id = a.question_id
    AND category_id = 1
    AND question_id
    BETWEEN (SELECT property FROM users WHERE email = '[e-mail]')
    AND (SELECT property FROM users WHERE email = '[e-mail]') + 14)
    
    UNION
    
(SELECT q.question,answers a
    WHERE q.id = a.question_id
    AND category_id = 2
    AND question_id
    BETWEEN (SELECT laws FROM users WHERE email = '[e-mail]')
    AND (SELECT laws FROM users WHERE email = '[e-mail]') + 16)
    
ORDER BY question_id,id

当前以以下格式返回结果的

：

+-----------------------------+-------------+-------------+--------+
|          question           | category_id | question_id | answer |
+-----------------------------+-------------+-------------+--------+
| What color is the sky?      |           1 |          16 | blue   |
| What color is the sky?      |           1 |          16 | green  |
| What color is the sky?      |           1 |          16 | purple |
| What color is the sky?      |           1 |          16 | red    |
| What color is a firetruck?  |           1 |          17 | orange |
| What color is a firetruck?  |           1 |          17 | teal   |
| What color is a firetruck?  |           1 |          17 | red    |
| What color is a firetruck?  |           1 |          17 | green  |
| What color is dirt?         |           2 |          18 | green  |
| What color is dirt?         |           2 |          18 | green  |
| What color is dirt?         |           2 |          18 | green  |
| What color is dirt?         |           2 |          18 | green  |
+-----------------------------+-------------+-------------+--------+

我想做的是根据category_id更改顺序，因此类别id会像这样交替排列：1、2、1,2，但是我想让组基于question_id。因此结果将如下所示：

+-----------------------------+-------------+-------------+--------+
|          question           | category_id | question_id | answer |
+-----------------------------+-------------+-------------+--------+
| What color is the sky?      |           1 |          16 | blue   |
| What color is the sky?      |           1 |          16 | green  |
| What color is the sky?      |           1 |          16 | purple |
| What color is the sky?      |           1 |          16 | red    |
| What color is dirt?         |           2 |          18 | green  |
| What color is dirt?         |           2 |          18 | green  |
| What color is dirt?         |           2 |          18 | green  |
| What color is dirt?         |           2 |          18 | green  |
| What color is a firetruck?  |           1 |          17 | orange |
| What color is a firetruck?  |           1 |          17 | teal   |
| What color is a firetruck?  |           1 |          17 | red    |
| What color is a firetruck?  |           1 |          17 | green  |
+-----------------------------+-------------+-------------+--------+

我尝试使用ORDER BY row_number() OVER (PARTITION BY t.category_id ORDER BY t.category_id) 但这只会导致每个数据都被交替，而没有按question_id分组

解决方法

我认为您想要以下order by子句：

order by 
    rank() over(partition by category_id order by question_id),question_id,id

基本上，这会交错类别/问题元组。

注意：

• 使用标准的显式联接（from ... join ... on），而不是老式的隐式联接（from ...,... where ...）；这是史前语法，不应在新代码中使用

• 您的查询很可能会简化为不使用union；如果您要提出另一个有关样本数据和所需结果的问题，也许可以提出建议