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Re: st: a question about merge


From   Philip Ryan <philip.ryan@adelaide.edu.au>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: a question about merge
Date   Fri, 03 Sep 2004 09:24:25 +0930

I think you are attempting a many:many relational join.  Try:

use file1
joinby ID using file2, unmatched(both)

This assumes that both files are sorted on ID.

Phil



At 04:16 PM 2/09/2004 -0700, you wrote:
Dear Stata support,

I have a question on merging two datasets.

Assume that I have two datasets as followings:

Master dataset is named "file1" and contains two variables:
    ID    var1
    A      1
    A      2
    B      3

The using dataset is named "file2: and also contains two variables:

   ID   var2
   A     4
   A     5
   A     6

I would like to merge these two files. I expect to get a new file
(file3) as followings:

  ID   var1  var2
  A      1    4
  A      1    5
  A      1    6
  A      2    4
  A      2    5
  A      2    6
  B      3    .


However, after I sort both datasets by ID and then type command:

        merge ID using file2.dta

The resulted file is not what I expected.

I was wondering why this happens? Can I use merge command to obtain the
file3? Thanks a lot,

Sincerely,

Jian Zhang
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Philip Ryan
Associate Professor,
Department of Public Health
Associate Dean (Information Technology)
Faculty of Health Sciences
University of Adelaide 5005
South Australia
tel 61 8 8303 3570
fax 61 8 8223 4075
http://www.public-health.adelaide.edu.au/
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