按IN值列表排序

我在PostgreSQL 8.3中有一个简单的SQL查询，它抓取了一堆注释。我在WHERE子句中为IN构造提供了一个排序的值列表:

SELECT * FROM comments WHERE (comments.id IN (1,3,2,4));

这将以任意顺序返回注释，在my中恰好是id，如1,2,3,4。

我希望结果行像in结构中的列表一样排序:(1,3,2,4)。如何实现这一目标?

当前回答

让我们对已经说过的内容有一个直观的印象。例如，你有一个带有一些任务的表:

SELECT a.id,a.status,a.description FROM minicloud_tasks as a ORDER BY random();

 id |   status   |   description    
----+------------+------------------
  4 | processing | work on postgres
  6 | deleted    | need some rest
  3 | pending    | garden party
  5 | completed  | work on html

并且您希望按状态对任务列表进行排序。 status是一个字符串值列表:

(processing, pending,  completed, deleted)

诀窍是给每个状态值一个整数，并以数字顺序排列列表:

SELECT a.id,a.status,a.description FROM minicloud_tasks AS a
  JOIN (
    VALUES ('processing', 1), ('pending', 2), ('completed', 3), ('deleted', 4)
  ) AS b (status, id) ON (a.status = b.status)
  ORDER BY b.id ASC;

这就导致:

 id |   status   |   description    
----+------------+------------------
  4 | processing | work on postgres
  3 | pending    | garden party
  5 | completed  | work on html
  6 | deleted    | need some rest

信贷@user80168

2019-07-11 21:15:53

其他回答

只是因为它很难找到，它必须被传播:在mySQL中，这可以做得更简单，但我不知道它是否适用于其他SQL。

SELECT * FROM `comments`
WHERE `comments`.`id` IN ('12','5','3','17')
ORDER BY FIELD(`comments`.`id`,'12','5','3','17')

2012-01-15 21:19:27

无序列，只适用于8.4:

select * from comments c
join 
(
    select id, row_number() over() as id_sorter  
    from (select unnest(ARRAY[1,3,2,4]) as id) as y
) x on x.id = c.id
order by x.id_sorter

2009-05-15 01:17:37

select * from comments where comments.id in 
(select unnest(ids) from bbs where id=19795) 
order by array_position((select ids from bbs where id=19795),comments.id)

这里，[bbs]是主表，它有一个名为ids的字段， id是存储注释的数组。id。

在postgresql 9.6中通过

2017-06-06 11:08:15

在Postgres 9.4或更高版本中，这是最简单和最快的:

SELECT c.*
FROM   comments c
JOIN   unnest('{1,3,2,4}'::int[]) WITH ORDINALITY t(id, ord) USING (id)
ORDER  BY t.ord;

WITH ORDINALITY was introduced with in Postgres 9.4. No need for a subquery, we can use the set-returning function like a table directly. (A.k.a. "table-function".) A string literal to hand in the array instead of an ARRAY constructor may be easier to implement with some clients. For convenience (optionally), copy the column name we are joining to ("id" in the example), so we can join with a short USING clause to only get a single instance of the join column in the result. Works with any input type. If your key column is of type text, provide something like '{foo,bar,baz}'::text[].

详细解释:

PostgreSQL unnest()与元素号

2016-02-17 12:37:41