how to calculate unique column values in mysql

Question

Here is my data

cardNo| userName| tablename| hours |  date 
1     |  a      |    a     |   12  |  12-06-2015 
1     |  a      |    a     |    5  |  11-06-2015 
2         


        

Answer 1

SELECT cardNo,userName, tablename, sum(hours) hours FROM Table_1 GROUP BY cardNo,userName,tablename