Postgresql Select 具有值 X 或 Y 的关联记录不存在的行

Question

我有 3 张桌子：

Table        columns
---------------------
items        id, name
variations   id, item_id
images       id, variation_id, type

image 有一个 variation 而 variation 有一个 item

我想找到 items 没有 images of type 4 or 5 (types are any integer 0 ..5 并且不能为 null)

下面的查询有效，但是它使用了 UNION 子查询带有 NOT IN 约束，我认为这是低效的 - 问题是因此，编写此查询的更有效方法是什么。

SELECT DISTINCT i.id, i.name 
FROM items i 
INNER JOIN variations v 
  ON v.item_id = i.id 
INNER JOIN images vi 
  ON vi.variation_id = v.id 
WHERE i.id NOT IN (SELECT i.id FROM items i 
                  INNER JOIN variations v 
                    ON v.item_id = i.id 
                  INNER JOIN images vi 
                    ON vi.variation_id = v.id 
                  WHERE vi.type = 4
                  UNION
                  SELECT i.id FROM items i 
                  INNER JOIN variations v 
                    ON v.item_id = i.id 
                  INNER JOIN images vi 
                    ON vi.variation_id = v.id 
                  WHERE vi.type = 5)

解决方案

根据 Gordons 下面的回答，最终解决方案是：

select i.*
from items i
where not exists (select 1
                  from variations v join
                       images im
                       on v.image_id = im.id
                  where v.item_id = i.item_id and i.type in (4, 5)
                 )
and exists (select 1
                  from variations v join
                       images im
                       on v.id = im.variation_id
                       where v.item_id = i.id)

Answer 1

I want to find items which don't have images of type 4 or 5

根据您的描述，这听起来像 not exists:

select i.*
from items i
where not exists (select 1
                  from variations v join
                       images im
                       on v.image_id = im.id
                  where v.item_id = i.item_id and i.type in (4, 5)
                 );

Answer 2

Gordon 使用聚合的答案的替代方法：

SELECT DISTINCT
    i.id,
    i.name 
FROM items i 
INNER JOIN variations v 
    ON v.item_id = i.id 
INNER JOIN images vi 
    ON vi.variation_id = v.id
GROUP BY
    i.id
HAVING
    COUNT(*) FILTER (WHERE vi.type IN (4, 5)) = 0;

请注意，上面假设 id 是 items table 中的主键列。如果不是，那么也许我们应该改用 GROUP BY i.id, i.name。

Postgresql Select 具有值 X 或 Y 的关联记录不存在的行

Postgresql Select Rows where associated record with value X or Y does not exist

sql

postgresql

union

inner-join

subquery