From: | Alex Howansky <alex(at)wankwood(dot)com> |
---|---|
To: | pgsql-sql(at)postgresql(dot)org |
Subject: | how to tell the difference between empty field and null field |
Date: | 1999-12-13 04:17:01 |
Message-ID: | Pine.LNX.4.20.9912122157220.18303-100000@net-srv-0001.bvrd.com |
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Thread: | |
Lists: | pgsql-sql |
Assuming a table such as this:
create table users (
user text,
password text,
name text,
domain text
);
...and data such as this:
insert into users values
('frank','zCeZ6f2f.NUKU','Frank Farley','domain.com');
insert into users values
('joe','QJixz/XLXvio2','Joe Blogg','');
insert into users values
('sam','kAdhVr3URa4Y.','Sam Stooge');
Note that joe has a blank domain field, while sam has none.
I want to know what users don't have a domain specified in their domain field.
But the query:
select * from users where domain = '';
only shows me joe, and the query:
select * from users where domain = null;
only shows me sam.
So, I use:
select * from users where domain = '' or domain = null;
Here's my question: if I have a zillion records in this table, and it's indexed
by user+domain, how can I run this query without losing the benefit of the
index?
--
Alex Howansky
alex(at)wankwood(dot)com
http://www.wankwood.com/
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Next Message | Tom Lane | 1999-12-13 05:14:20 | Re: [SQL] how to tell the difference between empty field and null field |
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