如何按照数组元素的顺序对查询结果进行排序？

Question

我在 Postgres 9.4 中有这个查询：

select id from question where id = any(
    array_cat(
        ARRAY[0,579489,579482,579453,561983,561990,562083]::integer[], 
        (select array(
            select id from question where id not in 
                (0,579489,579482,579453,561983,561990,562083)
            and status in (1, -1) 
            and created_at > 1426131436 order by id desc offset 0 limit 10 )
        )::integer[]
    )
)

它returns:

但是顺序不对。我需要根据子数组的结果排序的结果：

array_cat(
        ARRAY[0,579489,579482,579453,561983,561990,562083]::integer[], 
        (select array(
            select id from question where id not in 
                (0,579489,579482,579453,561983,561990,562083)
            and status in (1, -1) 
            and created_at > 1426131436 order by id desc offset 0 limit 10 )
        )::integer[]
    )

我该怎么做？

Answer 1

ORDER BY idx(your_array, your_element)

或

ORDER BY your_array # your_element

intarray

select id from question where id = any(
    array_cat(
        ARRAY[0,579489,579482,579453,561983,561990,562083]::integer[], 
        (select array(
            select id from question where id not in 
                (0,579489,579482,579453,561983,561990,562083) and status in (1, -1) 
                and created_at > 1426131436 order by id desc offset 0 limit 10 )
        )::integer[]
    ) 
) ORDER BY array_cat(
    ARRAY[0,579489,579482,579453,561983,561990,562083]::integer[], 
    (select array(
        select id from question where id not in 
            (0,579489,579482,579453,561983,561990,562083) and status in (1, -1) 
            and created_at > 1426131436 order by id desc offset 0 limit 10 )
    )::integer[]
) # id

Answer 2

基础知识：

PostgreSQL unnest() with element number

由于您使用的是 Postgres 9.4，因此您可以使用新的 WITH ORDINALITY:

WITH t AS (
   SELECT *
   FROM   unnest('{0,579489,579482,579453,561983,561990,562083}'::int[])
                  WITH ORDINALITY AS t(id, rn)
   )
(
SELECT id
FROM   question
JOIN   t USING (id)
ORDER  BY t.rn
)
UNION ALL
(
SELECT id
FROM   question
LEFT   JOIN t USING (id)
WHERE  t.id IS NULL
AND    status IN (1, -1) 
AND    created_at > 1426131436
ORDER  BY id DESC
LIMIT  10
);

解释一下

因为您使用了同一个数组两次，所以我在查询前添加了一个 CTE，您可以在其中提供数组 once. unnest()它立即WITH ORDINALITY根据数组元素的顺序得到行号（rn）。
与其将你的子查询塞进一个数组然后再转换回来，不如直接使用它。便宜得多。排序顺序直接来自 id。
而不是使用 NOT IN 从给定数组中排除 ID（这对于 NULL 值可能很棘手）使用 LEFT JOIN / IS NULL:
- Select rows which are not present in other table
只需在这两部分后面加上UNION ALL。 UNION ALL 查询的每条腿上的括号必须有单独的 ORDER BY：
- Sum results of a few queries and then find top 5 in SQL
最后SELECT中的JOIN到question现在是多余的，我把它去掉了。

如何按照数组元素的顺序对查询结果进行排序？

How to order query result according to the order of array elements?

sql

postgresql

sql-order-by

unnest

set-returning-functions

解释一下