I have the following data:

A B
Inv No. Serial No.
0001 ABC
0001 DEF
0001 GHI
0002 JKL
0002 MNO
0002 PQR

and need to come back to this:

Inv No. Serial No
0001 ABC, DEF, GHI
0002 JKL, MNO, PQR


Would anyone be able to help me out