Finding distinct count of combination of columns values in sql

Question

Currently I have a table this :

Roll no.   Names
------------------
  1        Sam
  1        Sam 
  2        Sasha 
  2        Sasha 
  3        Joe
  4        Jack 
  5        Jack 
  5        Julie 

I want to write a query in which I get count of the combination in another column

Required output

Combination    distinct count 
-----------------------------
2-Sasha             1
5-Jack              1
5-Julie             1 

Answer 1

Basically, you could group by these columns and use a count function:

SELECT   rollno, name, COUNT(*)
FROM     mytable
GROUP BY rollno, name

You could also concat the two columns:

SELECT   CONCAT(rollno, '-', name), COUNT(*)
FROM     mytable
GROUP BY CONCAT(rollno, '-', name)