Code:
input file name: input_20100221.csv
20100221, abc_1, 200
20100221, abc_4, 300
20100221, opq_3, 200
20100221, abc_5, 200
20100221, xyz_1, 500
20100221, abc_2, 500
20100221, abc_3, 100
20100221, xyz_2, 700
20100221, opq_2, 300
20100221, xyz_3, 100
20100221, opq_1, 200
input file name: input_20100222.csv
20100222, abc_1, 100
20100222, abc_4, 200
20100222, opq_3, 200
20100222, abc_5, 200
20100222, xyz_1, 100
20100222, abc_2, 200
20100222, abc_3, 100
20100222, xyz_2, 200
20100222, opq_2, 800
20100222, xyz_3, 600
20100222, opq_1, 700
input file name: input_20100224.csv
20100224, abc_1, 600
20100224, abc_4, 400
20100224, opq_3, 200
20100224, abc_5, 300
20100224, xyz_1, 300
20100224, abc_2, 200
20100224, abc_3, 700
20100224, xyz_2, 200
20100224, opq_2, 200
20100224, xyz_3, 900
20100224, opq_1, 800