state    month          ID      sales
-------------------------------------
FL       05/18/2015     0001   12,000
FL       05/19/2015     0001    6,000
FL       05/20/2015     0001    3,000
FL       05/21/2015     0001    6,000
FL       06/01/2016     0001    4,000  
TX       06/02/2016     0050    1,000
In the above table month column having same month but with different date. My question is how to add/sum of sales column having same month with different dates?
 
     
     
     
     
     
     
    