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From: Henry Ortega <juandelacruz@gmail.com>
To: pgsql-sql@postgresql.org
Subject: Fastest way to get max tstamp
Date: Mon, 28 Aug 2006 14:10:02 -0400
Message-ID: <2bffcc330608281110j404e3fd1q9d6d27a6a97ad31d@mail.gmail.com> (raw)

This is my table:
 name | program | effective  |           tstamp           | rate
------+---------+------------+----------------------------+------
 jdoe | AAA     | 2006-07-01 | 2006-07-16 23:42:13.809214 |   20
 jdoe | BBB     | 2006-07-01 | 2006-07-16 23:42:13.809214 |   20
 jdoe | AAA     | 2006-08-16 | 2006-08-25 11:56:50.380575 |   20
 jdoe | BBB     | 2006-08-16 | 2006-08-25 11:56:50.380575 |   20
 jdoe | AAA     | 2006-08-16 | 2006-08-25 11:57:17.394854 |   20
 jdoe | BBB     | 2006-08-16 | 2006-08-25 11:57:17.394854 |   20
 jdoe | AAA     | 2006-09-01 | 2006-08-28 12:38:42.486513 |   20
 jdoe | BBB     | 2006-09-01 | 2006-08-28 12:38:42.486513 |   20

I want to get:
 name | program | effective  |           tstamp           | rate
------+---------+------------+----------------------------+------
 jdoe | AAA     | 2006-07-01 | 2006-07-16 23:42:13.809214 |   20
 jdoe | BBB     | 2006-07-01 | 2006-07-16 23:42:13.809214 |   20
 jdoe | AAA     | 2006-08-16 | 2006-08-25 11:57:17.394854 |   20
 jdoe | BBB     | 2006-08-16 | 2006-08-25 11:57:17.394854 |   20
 jdoe | AAA     | 2006-09-01 | 2006-08-28 12:38:42.486513 |   20
 jdoe | BBB     | 2006-09-01 | 2006-08-28 12:38:42.486513 |   20

Basically, for effective='08-16-2006', it only gets the latest inserted
record (using tstamp) for that effective date, which is 2006-08-25 11:57:
17.394854.

So what is the quickest way to do this?
I can always do:
Select * from Table t where tstamp=(select max(tstamp) from Table t2 where
t2.name=t.name and t2.effective=t.effective)
but it takes so long since this is a huge table.

Any suggestions?

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