Break combine column data into rows
# For example, separate the following content:
# David cat,dog
# into
# David cat
# David dog
awk '{split($2,a,",");for(i in a)print $1"\t"a[i]}' file
# Detail here: http://stackoverflow.com/questions/33408762/bash-turning-single-comma-separated-column-into-multi-line-string