SQL for joining 2 tables but a bit complicated for my understanding - oracle-sqldeveloper

Question

Got a situation thats a bit beyond my understanding.
Table A has the Product, Country and Factory
Table B has the Product, Factory and city.
The scenario is such that sales forecast data flows from the country level via the factory and then to city level. We have factories only in Rotterdam and Amsterdam. The issue is such that the factories in Table A need to be the same as the factory in table B.
I have to clean data for situations C&D where the factories in Table A are wrong and need cleaning. I therefore first need to identify these wrong records:
Here is what I got so far by joining Table A and B
select A.Prod,A.country,A.factory,B.Prod,B.factory,B.City from Table1 A, Table2 B where and A.Prod=B.Prod and A.Factory <>B.Factory
Of course I can find a specific known wrong record by using below SQL, but I need to find for all wrong records without specifying any product or
select A.Prod,A.country,A.factory,B.Prod,B.factory,B.City from Table1 A, Table2 B where A.Prod=B.Prod and A.Factory <>B.Factory
and A.Country ='Norway' and A.Factory ='Rotterdam' and B.City ='Oslo'
Situation 1
Table A
Product Country Factory
ProdA Switzerland Rotterdam
Table B
Product Factory City
ProdA Rotterdam Geneva
Situation 2
Table A
Product Country Factory
Prod Germany Rotterdam
Table B
Product Factory City
ProdB Rotterdam Dresden
Situation 3
Table A
Product Country Factory
ProdC Norway Rotterdam
Table B
Product Factory City
ProdC Amsterdam Oslo
Situation 4
Table A
Product Country Factory
ProdD Finland Rotterdam
Table B
Product Factory City
ProdD Amsterdam Helsinki

Answer 1

From what I understand Your projection for the country in Table A, has to be for a city in table B, which exists in the country in table A.
So, in situation 1, we have
Table A country = Switzerland, Table B city = Geneva.
Since, Geneva is in Switzerland, this is fine
In situation 2, we have
Table A country = Germany, Table B city = Dresden
Since Dresden is in Germany this is fine.
This gives us a clue on how we can attack the problem.
Step 1. Setup a table for your expected country/city
CREATE TABLE COUNTRY_CITY (COUNTRY VARCHAR(60), CITY VARCHAR(60));
STEP 2. Insert the values for expected country/city into table
INSERT INTO COUNTRY_CITY(COUNTRY,CITY) VALUES('GERMANY','DRESDEN');
INSERT INTO COUNTRY_CITY(COUNTRY,CITY) VALUES('SWITZERLAND','GENEVA');
INSERT INTO COUNTRY_CITY(COUNTRY,CITY) VALUES('NORWAY','OSLO');
INSERT INTO COUNTRY_CITY(COUNTRY,CITY) VALUES('FINLAND','HELSINKI');
STEP 3.
select A.Prod,A.country, A.factory, B.Prod, B.factory, B.City,
COUNTRY_CITY.CITY
from
Table1 A
INNER JOIN Table2 B ON A.Prod=B.Prod
INNER JOIN COUNTRY_CITY ON A.COUNTRY = COUNTRY_CITY.COUNTRY
where COUNTRY_CITY.CITY = B.city and A.Factory <> B.Factory
So in step 3, we give the database the knowledge of which city belongs to which country, so that we can do a join from Table A to table B. Once you get that, then the condition on the not matching factories should be the records that you are looking for