Dryice Liu's Blog » postgresql

mysql tip: finding duplicated records

dryice — Wed, 24 Sep 2008 02:43:00 +0000

Found here: http://mysql-tips.blogspot.com/2005/04/mysql-find-duplicate-repords-example.html

select address, count(address) as cnt
from mailing_list
group by address
having cnt > 1
order by cnt;

sqlite doesn’t support more than one primary key in one table

dryice — Mon, 28 Aug 2006 13:03:00 +0000

This cost me several hours today.

Postgresql support multiple primary keys in one table, and I took granted that sqlite does the same thing when I did some prototype today.

And they have a good reason explained in the SQLite CVSTrac.

The odd thing is, if I specify two primary keys in sqlite, it won’t complain when creating the table, but complains that one of the primary key can’t be NULL when I do a insert. This lead me to a wrong way

The solution is easy when I found the problem: use the unique keyword instead of primary key.

don’t create table with name ends "_seq"

dryice — Sun, 13 Jun 2004 22:43:00 +0000

postgresql use this kind of table to keep track of sequence.