st: Merging database

["SERGIO M. AFCHA CHÁVEZ" <s.afcha@ub.edu>]

Dear Statlisters,

I have a little problem merging a data base. I have variables for 3 
years showing an ID:

V1  V2  V3
1     .       1
2     .       2
3    3       3
4    4        .   
.     5       5
6     .       6


I need only one ID variable. How can I obtain one column with  all the 
ID numbers?
Thanks in advance for your help.

Sergio 

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