On Wed, Feb 13, 2013 at 3:01 PM, Andrew Taylor <andydtaylor@gmail.com> wrote:
> And ended up with a table 13,708,233 rows long with what looks like plenty
> of duplicated rows. Some but not all are duplicated. What can I do to sort
> this out?
It means that (e, n) pairs are not unique in A and B and you got a
superposition of them. If you have 5 equal pairs in A and 7 same pairs
with in B you will get 35 combinations as a result.
And BTW when you use LEFT JOIN if there are rows in A that have no
matching pairs in B you will get one row for each of them where lan
and lon are NULLs.
See the join_type section here
http://www.postgresql.org/docs/9.2/static/sql-select.html.
--
Sergey Konoplev
Database and Software Architect
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