ODBC SELECT WHERE a IN ('frob') returns where a = '' too

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POSTGRESQL BUG REPORT TEMPLATE
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Your name : Adam Haberlach
Your email address : adam(at)be(dot)com

System Configuration
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Architecture (example: Intel Pentium) : Intel Pentium

Operating System (example: Linux 2.0.26 ELF) :Linux version 2.2.2

PostgreSQL version (example: PostgreSQL-6.5.1): PostgreSQL-7.0

Compiler used (example: gcc 2.8.0) : gcc version 2.7.2.3

Please enter a FULL description of your problem:
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When I do a query of the form

SELECT a FROM tbl WHERE a IN ('frob');

where a is an indexed text field containing 'frob', 'dingus', '', and
NULL

I get a set that includes rows both where
a == 'frob'
a == ''

This happens when I use ODBC from Microsoft Access's pass-through, but
does not seem to happen from the psql
command-line. This seems to confuse my coworker who is more familiar
with non-Postgres databases then I.

--
Adam Haberlach |"You have to understand that the
adam(at)newsnipple(dot)com | entire 'Net is based on people with
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