All you need is "cat" + "sort"
Example---I generated 2 files--join1 and join 2:
Code:
[mherring@Ath play]$ cat join1
1 aaasdg
5 sadfooin
5 asdb
8 asdoihn
[mherring@Ath play]$ cat join2
31 oipiou
1 oibswetasd
9 the horse
2 the pig
[mherring@Ath play]$ cat join1 join2|sort -n
1 aaasdg
1 oibswetasd
2 the pig
5 asdb
5 sadfooin
8 asdoihn
9 the horse
31 oipiou