what about join

join file1 file2

try this

cat file3 | tr "\n" "\t" > file4

join FILE1.dat FILE2.dat | tr "\n" "\t" > file4

Hi,
I just try both of the code that you suggested.
End up It will link all the data together and generated the output like this:
1285_t chris germany 8288_c steve england 9626_a dave swiss
Do I did anything wrong?
Thanks again, frans

You did allright
I think your awk script looks good. I couldn't do better

Never mind.
Knowledge is sharing ^^

Something like this :

awk 'NR==FNR{a[$1]=$1;next} { if($1 in a) print }' f1 f2

If it is too slow, you could test if awk runs faster. Especially mawk is lightning quick.

awk 'NR==FNR{a[$1]=1;next}a[$1]' file1 file2>file3