在Postgres 9.4中，这可以做得更短一些:

select c.*
from comments c
join (
  select *
  from unnest(array[43,47,42]) with ordinality
) as x (id, ordering) on c.id = x.id
order by x.ordering;

或者在没有派生表的情况下更加紧凑:

select c.*
from comments c
  join unnest(array[43,47,42]) with ordinality as x (id, ordering) 
    on c.id = x.id
order by x.ordering

无需手动为每个值分配/维护位置。

在Postgres 9.6中，可以使用array_position():

with x (id_list) as (
  values (array[42,48,43])
)
select c.*
from comments c, x
where id = any (x.id_list)
order by array_position(x.id_list, c.id);

使用CTE时，值列表只需要指定一次。如果这并不重要，也可以写成:

select c.*
from comments c
where id in (42,48,43)
order by array_position(array[42,48,43], c.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

相比使用序列的版本略有改进，我认为:

CREATE OR REPLACE FUNCTION in_sort(anyarray, out id anyelement, out ordinal int)
LANGUAGE SQL AS
$$
    SELECT $1[i], i FROM generate_series(array_lower($1,1),array_upper($1,1)) i;
$$;

SELECT 
    * 
FROM 
    comments c
    INNER JOIN (SELECT * FROM in_sort(ARRAY[1,3,2,4])) AS in_sort
        USING (id)
ORDER BY in_sort.ordinal;

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')

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

在Postgresql:

select *
from comments
where id in (1,3,2,4)
order by position(id::text in '1,3,2,4')