SQL function to list a column across tables without primary key

Question

I have a table listing states and one with cities, with State_number acting as a foreign key in the cities table. Is it possible to list the cities via their state name?

This is the closest I have gotten:

SELECT State_name, City_name 
FROM States, Cities 
JOIN Cities on States.State_number = Cities.State_number
WHERE States.State_name IN ('Munich', 'Brandenburg');

An example of the current output:

State_name
City_name
Bavaria
Munich

Bavaria 
Nuremburg

Brandenburg
Berlin

Whereas I am hoping for something like:

Munich
7
Brandenburg
10

Answer 1

Just join them and apply a WHERE clause:

select st.state_name, c.city_name
from states s
  join cities c on s.state_number = c.state_number
where s.state_name = 'Bavaria';

To get the count of cities per state (which wasn't part of the original question), you can use a group by

select st.state_name, count(*) as number_of_cities
from states s
  join cities c on s.state_number = c.state_number
where s.state_name in ('Brandenburg','Bavaria')
group by st.state_name;

Answer 2

I think you want:

SELECT s.State_name, c.City_name 
FROM States s JOIN
     Cities c
     ON s.State_number = c.State_number
WHERE c.City_name IN ('Munich', 'Brandenburg');

Notes:

• Never use commas in the FROM clause.
• Always use proper, explicit, standard , readable JOIN syntax.
• Use table aliases! And qualify all column references!
• Your filter should be on the city name not the state name. I think that is the fundamental issue with your version of the query.