MySQL Inner Join Query To Get Records Not Present in Other Table

Question

I have table 1, all_countries, as follows-

id   |  country
------------------
1    |  USA
2    |  China
3    |  India
4    |  France
5    |  UK
6    |  Australia         


        

Answer 1

A LEFT JOIN will do that elegantly;

SELECT a.* 
FROM all_countries a
LEFT JOIN supported_countries s
  ON a.country = s.country
WHERE s.id IS NULL;

Demo here.