sql - Postgresql - 从选择中删除元素的 Array_remove

Question

我有一个列(成员)，其中包含一个包含不同数量元素的数组。

例如

id   members (integer[])
1    {1, 3, 5, 7}
2    {4, 5, 7, 9}

我有一个表 (unwanted_members)，其中包含我希望删除的成员(如果存在的话)，例如

member
1
7

我想从数组中删除这些成员，即

id  members
1   {3, 5}
2   {4, 5, 9}

谁能推荐一个简单的方法？

Answer 1

如果安装 intarray扩展这很容易:

select id, members - (select array_agg(member) from unwanted_members)
from foo;

要更新表格，您可以使用:

update foo
    set members = members - (select array_agg(member) from unwanted_members);

---

如果没有该扩展，您首先需要取消成员 ID 的嵌套，移除不需要的，然后将它们聚合回一个数组:

select f.id, array_agg(t.mid order by t.idx) as members
from foo f, unnest(f.members) with ordinality as t(mid,idx)
where t.mid not in (select member from unwanted_members)
group by f.id;

要更新现有值，请使用:

update foo
  set members = x.members
from (
  select f.id, array_agg(t.mid order by t.idx) as members
  from foo f, unnest(f.members) with ordinality as t(mid,idx)
  where t.mid not in (select id from unwanted_members)
  group by f.id
) x
where foo.id = x.id;

假设id是表的主键。