How to count rows that have the same values in two columns (SQL)?

Question

I am sure there must be a relatively straightforward way to do this, but it is escaping me at the moment. Suppose I have a SQL table like this:

+-----+-----         


        

Answer 1

This could be the answer:

SELECT a, b, COUNT(*) 
FROM  
GROUP BY a,b 
ORDER BY 3 DESC;