Question

假设我们拥有标题，职位和来源的产品。

我需要按字符串模式“basse”订购产品。订购产品后应如下：

id  title   source  position
9   prod 9  b   0
1   prod 1  a   0
13  prod 13 s   0
14  prod 14 s   1
5   prod 5  e   0
10  prod 10 b   1
2   prod 2  a   1
15  prod 15 s   2
16  prod 16 s   3
6   prod 6  e   1
11  prod 11 b   2
3   prod 3  a   2
7   prod 7  e   2
12  prod 12 b   3
4   prod 4  a   3
8   prod 8  e   3

Answer 1

select id, title, source, position
from (
    select id, title, source, position, new_source,
        case new_source
            when 'b' then 0
            when 'a' then 1
            when 's' then 2
            when 't' then 3
            else 4
        end as pos
    from (
        select id, title, source, position,
            case 
                when source <> 's' then source
                when (row_number() over w % 2)::int::bool then 's'
                else 't'
            end as new_source
        from products
        window w as (partition by source order by position)
        ) s
    ) s
window w as (partition by new_source order by position)
order by (row_number() over w)* 5+ pos;

Test it here.

Answer 2

您只能通过排序来实现这一目标。相反，创建一个PL / pgSQL函数“basse（）”，它返回一组setof记录。在函数内部，为b，a，s，e声明四个未绑定的产品％rowtype数组，并打开游标迭代产品。将每个读取的产品放在相应的数组中。然后插入数组，从正确的数组返回一个元素（如果不是空的话）。最后在函数结束时调用RETURN。要使用该功能，请执行SELECT * FROM basse（）

按字符串模式的Postgresql订单记录

2 个答案: