SQL: How do you select only groups that do not contain a certain value?

Question

Say I have a table:

Restaurant locations: 

RESTAURANT_NO | RESTAURANT_LOCATION
-----------------------------------
1             |            City A
1               


        

Answer 1

SELECT DISTINCT
      Restaurant_no
FROM 
      TableX t
WHERE 
      NOT EXISTS
      ( SELECT *
        FROM TableX c
        WHERE c.Restaurant_no = t.Restaurant_no
          AND c.Restaurant_location = 'City C'
      )