Question insert data

Hi There,

I've a problem with inserting data and I can't figure out what the problem
is:

what did I do:

1. I've a master table containing about 40000 records. A count(*) provides
me the exact number.

2. I've create a table based on from the master. I copied a fraction from
the master into the new table using a where clause (insert into ... select
* from ... where a = b . The number of records copied is about 2553.

Issueing the same select statement on the master table gives me a list of
5106 which is twice the number of copied records.

Did someone have this problem before?

I'm using 8.0 Windows XP en the pgAdmin III , r1.2.0

I even tried the same on the command line!

thanks,
Peter

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