Only show Warehous where product is not existing – multiply tables mysql

I’ve got three tables. Product, Warehouse and IsIn.

Product:

• productID
• name
• price

Warehouse:

• warehousID
• name

IsIn:

• productID*
• warehousID*
• quantity

I now want to write a question where i get all warehouses where a specific product does not exist.

I can get a table where the specific product are, but when i try to get where it’s not, I get the wrong answer.

Does anyone know how i can write the question?

Answer

I now want to write a question where i get all warehouses where a specific product does not exist.

This sounds like a NOT EXISTS query:

select w.*
from warehouse w
where not exists (select 1
                  from isin i
                  where i.warehouseid = w.warehouseid and
                        i.productid = ?
                 );

You may want to add and i.quantity > 0 in the subquery. It is not clear if quantity is important for the question.