create sequence serial start 1;

select * from comments c
join (select unnest(ARRAY[1,3,2,4]) as id, nextval('serial') as id_sorter) x
on x.id = c.id
order by x.id_sorter;

drop sequence serial;

(编辑)

Unnest在8.3中还没有内置，但你可以自己创建一个(任何的美丽*):

create function unnest(anyarray) returns setof anyelement
language sql as
$$
    select $1[i] from generate_series(array_lower($1,1),array_upper($1,1)) i;
$$;

该函数可以在任何类型下工作:

select unnest(array['John','Paul','George','Ringo']) as beatle
select unnest(array[1,3,2,4]) as id

在Postgres中另一种方法是使用idx函数。

SELECT *
FROM comments
ORDER BY idx(array[1,3,2,4], comments.id)

不要忘记首先创建idx函数，如下所述:http://wiki.postgresql.org/wiki/Array_Index

你可以很容易地使用(在PostgreSQL 8.2中引入)VALUES()，()。

语法是这样的:

select c.*
from comments c
join (
  values
    (1,1),
    (3,2),
    (2,3),
    (4,4)
) as x (id, ordering) on c.id = x.id
order by x.ordering

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

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

通过进一步研究，我发现了这个解决方案:

SELECT * FROM "comments" WHERE ("comments"."id" IN (1,3,2,4)) 
ORDER BY CASE "comments"."id"
WHEN 1 THEN 1
WHEN 3 THEN 2
WHEN 2 THEN 3
WHEN 4 THEN 4
END

然而，这似乎相当冗长，并且对于大型数据集可能会有性能问题。 有人能就这些问题发表评论吗?