Key Matching using shell

Question

I wanted to see different type of answers I receive from you guys for the below problem. I am curious to see below problem being solved completely through array or any other

Answer 1

Try this:

awk -F', ' '{a[$1]=a[$1]","$2}END{for(i in a) print i a[i]}' input.txt

Output:

Name1,Phone1,Phone2
Name2,Phone2,Phone1
Name3,Phone1
Name4,Phone5,Phone1