Hi!
select * from any where is_deleted = Null
select * from any where is_deleted in (Null)
They are show 0 record.
select * from any where is_deleted is Null
It is show all records.
Some of other DBs are uses Null as Null in = comparisons. Is PG not? What
are the rules?
Thanks: dd
On Jul 8, 2009, at 1:30 PM, Durumdara wrote:
Hi!
select * from any where is_deleted = Null
select * from any where is_deleted in (Null)
They are show 0 record.
Correct, that's normal in SQL.
NULL means 'unknown', so you can't say whether is_deleted is true or
false when it's NULL. The
Durumdara durumd...@gmail.com writes:
Some of other DBs are uses Null as Null in = comparisons. Is PG not?
What are the rules?
PostgreSQL implements SQL, which has a 3-valued logic. There's True,
there's False, and there's NULL. NULL means that we know nothing about
what's in there.
Would you
On Wed, Jul 8, 2009 at 6:03 AM, Alban
Hertroysdal...@solfertje.student.utwente.nl wrote:
This is exactly the reason the 'is null' operator exists. It's exclusively
for checking for null values. You can't say 'is_deleted is true' for
example.
Uh, yes you can. is false also works. and is not
Some DB's say that an empty string is the same as null, it doesn't mean
they're right. In fact, it can be rather inconvenient if an empty string
in your data also has a meaning (namely 'known to be an empty string'
instead of 'unknown')!
This is the behavior in Oracle. And I found that out
I'm (1) new to postgres (2) trying to "convert" the sample db found
in "The Practical SQL Handbook" Bowman, et al. to postgres. When
trying to create the following table I get "parser: parse error at or
near 'null'"
create table authors (
au_id char(11)not null,
