Question

我有一张包含2条记录的表（说明目的）

| id      | access (int array) |
| ---------------------------- |
| 1       | {0,1,0}            | 
| 2       | {1,0,0}            |

我想选择两个值并将它们合并在一起在这种情况下获得最高价值的结果：

{1,1,0}

访问阵列可能会增长到超过200个值，因此我想避免在编程代码中执行此操作（golang）。

基本上它与这个问题相同：Merge two (or more) arrays and keep values that are highest?但在我的情况下，分隔的列被组合成一个带有数组的字段。

更新

row(access)数组总是具有相同数量的值

Answer 1

尝试此查询（SqlFiddle）：

select array_agg(elem)
from (
    select distinct on (row_number) row_number, elem 
    from (
        select id, elem, row_number() over (partition by id)
        from (
            select id, unnest(access) elem
            from merge_test
            where id in (1,2)
            ) sub
        ) sub
    order by 1, 2 desc
    ) sub;

二进制数组

如果数组只包含＆＃39; 0＆＃39;和＆＃39; 1＆＃39;并且具有相同数量的值：

create table merge_binary_test (id int, access int[]);
insert into merge_binary_test values
(1, '{0,1,0,1}'),
(2, '{1,0,0,1}');

select string_to_array(bit_or(elem)::text, null)::int[]
from (
    select id, array_to_string(access, '')::varbit elem
    from merge_binary_test
    where id in (1,2)
    ) sub

 string_to_array
-----------------
 {1,1,0,1}
(1 row)

Answer 2

请考虑以下为例：

create table arr(id int,access int[]);
insert into arr values (1,'{0,1,0}'),(2,'{0,1,0}'),(3,'{0,0,9}');

这样行将是：

id access  
-- ------- 
1  {0,1,0} 
2  {0,1,0} 
3  {0,0,9}

现在可以创建一个函数来合并数组行，如下所示：

CREATE
    OR replace FUNCTION merge_array (
    arrval INT -- the total number of values in an array in my example its 3, but 200 is for yours
    ,tbl TEXT --name of the table in which you want perform this function,
    ,col TEXT -- name of the array col
    )
RETURNS setof INTEGER [] AS $$

DECLARE qry TEXT;

BEGIN
    SELECT format('select translate(string_to_array(x.*::text,'','')::text,''()'','''')::int[] from (select %s  from (select ' || col || ' ar  from  ' || tbl || ' ) as sq) as x ', egn)
    INTO qry
    FROM (
        SELECT string_agg('max(ar[' || val || '])', ',') egn
        FROM (
            SELECT generate_series(1, arrval) val
            ) t
        ) tt;

    RETURN QUERY

    EXECUTE (qry);
END;$$

LANGUAGE plpgsql

用法：select merge_array(3,'arr','access') 结果：

merge_array 
----------- 
{0,1,9}

PostgreSQL：加入2个最大值为

2 个答案: