st: Puzzling error with merge

[David Hoaglin <dchoaglin@gmail.com>]

Dear All,

I attempted to merge two datasets, each of which has 247 observations,
with the following command:

merge 1:1 StudyID using Sheet2

(here "Sheet2" is the last part of the fully qualified name of the
file, recently imported from Excel).

I received the following error message: "variable StudyID does not
uniquely identify observations in the master data".

I then tabulated StudyID in the two files.  Each output showed no
frequency other than 1 and a total of 247 observations.

What am I doing wrong?

I am using Stata 13.1.

Thanks for your help.

David Hoaglin
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