for example I have record with three columns: id, customer1, customer2
original data as following
1; A1; A2
2; A1; A3
3; A2; A3
may I know is it possible converting into two columns structure: id, customer
data will become
1; A1
1; A2
2; A1
2; A3
3; A2
3; A3
sequence is not important
thanks