Merge two data sets A & B into one

Please help. How can I merge the 2 sets into one as shown below ? Tried "consolidate" function but not successful.
Thanks.
set A
1-Jan-12 a
2-Jan-12 a
3-Jan-12 a
4-Jan-12 a
5-Jan-12 a
6-Jan-12 a
7-Jan-12 a
Set B
1-Jan-12 b
2-Jan-12 b
3-Jan-12 b
4-Jan-12 b
5-Jan-12 b
6-Jan-12 b
7-Jan-12 b
8-Jan-12 b
9-Jan-12 b



merged set
1-Jan-12 a b
2-Jan-12 a b
3-Jan-12 a b
4-Jan-12 a b
5-Jan-12 a b
6-Jan-12 a b
7-Jan-12 a b
8-Jan-12 b
9-Jan-12 b

a and b are in 2 separate columns.