st: merge multiple database

["Yun Liu" <liuyun3@gmail.com>]

Hi, I am trying to merge multiple database and keep specific variables
from each of the using files.
I type "merge id using db1 db2, keep(var1 var2)".  var1 is in db1 and
var2 is in db2. But stata gives an error message: "variable var2 not
found in using dataset." Please help. Thank you!
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