Bagaimana Anda memeriksa nilai yang cocok di kolom ketiga berdasarkan kombinasi berbeda dari dua kolom lainnya?

Anda dapat group by building, location untuk baris where object in ('WALL', 'WINDOW') :

select building, location, 'FLAG' action
from tablename
where object in ('WALL', 'WINDOW')
group by building, location
having count(distinct object) < 2

Kondisi count(distinct object) < 2 di having klausa mengembalikan kombinasi building, location di mana 'WALL' dan 'WINDOW' keduanya tidak ada.
Lihat demo .
Hasil:

| building | location | action |
| -------- | -------- | ------ |
| A        | FLOOR2   | FLAG   |
| B        | FLOOR1   | FLAG   |

Atau dengan NOT EXISTS:

select t.building, t.location, 'FLAG' action
from tablename t
where object in ('WALL', 'WINDOW')
and not exists (
  select 1 from tablename
  where building = t.building and location = t.location and object <> t.object
)

Lihat demo .