Using awk to find the sum of a CSV file after group by on a particular column

http://www.theunixschool.com/2012/06/awk-10-examples-to-group-data-in-csv-or.html

I have a CSV file like :


65523 , 100
65522 , 900
65522 , 1800
65522 , 100
65522 , 100
65521 , 500
65521 , 200
65521 , 200

I need to find the sum of the 2nd column based on the grouping by the 1st column, so that the output looks something like:


65523 , 100
65522 , 2900
65521 , 900

SOLUTION:

This can be easily achieved using a single line awk script:

awk -F"," '{a[$1]+=$2;}END{for (i in a)print i, a[i];}' file

Awesome isn't it !! :)