Create array from csv file.

Hi everyone. 

I have a csv file, im trying to read and output the number of unique row according to second column. 

csv file : 

2013-03-25 00:00:06,"00:0E:6D:3F:D5:76","-68","5374468","B"

2013-03-25 00:00:07,"04:A8:2A:18:8A:04","-66","5898756","B"

2013-03-25 00:00:08,"00:0E:6D:3F:D5:76","-68","5374468","B"

so the output of the csv file should be 2.

I appreciate any help thanks .