连接 2 个表 (a, b) 并返回 (b) 中的 NULL 值

Question

I would like to join 2 tables (a, b) and returning values that are NULL in (b). I'm working with 2 tables -- called cookies and all_desserts . Cookies exist in all_desserts , but I want to get a table that displays values of all_desserts.names - cookies.names .

Essentially, I want to show all the desserts in the desserts table that are NOT cookies. I think I need to use null here and a right join. I would like to call this new table desserts_without_cookies .

Here is what I have so far (which doesn't work). Am I doing the wrong type of join?

FROM cookies LEFT JOIN desserts.cookies ON cookies.cookie_name = desserts.cookies
WHERE desserts.cookies IS NULL```

Answer 1

You can do it with NOT EXISTS :

select ad.*
from all_deserts ad
where not exists (select 1 from cookies c where c.names = ad.names)

A LEFT JOIN would also work:

select ad.*
from all_deserts ad left join cookies c 
on c.names = ad.names
where c.names is null