-Original Message-
From: [EMAIL PROTECTED] [mailto:pgsql-general-
[EMAIL PROTECTED] On Behalf Of Emi Lu
Sent: Wednesday, March 08, 2006 2:52 PM
To: pgsql-general@postgresql.org
Subject: [GENERAL] column type varchar(128) not null default '' vs
varchar(128)
Hello,
When setuping column types, is there the big efficiency difference
between the following two examples?
col varchar(128) NOT NULL default ''
vs.
col varchar(128)
The difference has nothing to do with efficiency and everything to do
with what goes into them.
The first example does not allow col to be NULL. If you insert a row
and do not insert any data into column col, col will get a value of ''
(empty) which is not the same thing as NULL.
The second example does not have a default and allows NULL values. So
if you insert data into the table in the second example, and you do not
provide data for column col, then col will be NULL.
---(end of broadcast)---
TIP 9: In versions below 8.0, the planner will ignore your desire to
choose an index scan if your joining column's datatypes do not
match