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?