Postgres重叠一列的数组

Question

我有一个表"A",其中一列"col1",其中每个记录是一个整数数组.

col1
-----
{1,2,3,4}
{1,2,6,7}
{1,2,3,8,9}

我喜欢有一行结果,其中包含"col1"中所有数组的重叠或交叉.

select overlap(col1) from A;

result
-----
{1,2}

Answer 1

您应该为此目的定义自定义聚合:

CREATE OR REPLACE FUNCTION public.overlap_array_aggregate(anyarray, anyarray)
 RETURNS anyarray
 LANGUAGE plpgsql STRICT
AS $function$
BEGIN
  RETURN ARRAY(SELECT unnest($1) INTERSECT SELECT unnest($2));
END;
$function$

CREATE AGGREGATE array_overlap_agg (
   basetype = anyarray,
   sfunc =  overlap_array_aggregate,
   stype = anyarray );

然后它按预期工作:

postgres=# SELECT * FROM foo;
???????????????
?      a      ?
???????????????
? {1,2,3,4}   ?
? {1,2,6,7}   ?
? {1,2,3,8,9} ?
???????????????
(3 rows)

postgres=# SELECT array_overlap_agg(a) FROM foo;
?????????????????????
? array_overlap_agg ?
?????????????????????
? {1,2}             ?
?????????????????????
(1 row)