Hi,
is the empty array representable in PostgreSQL, and is it
distinguishable from NULL?
oocms=# SELECT ARRAY[1, 2];
array
---
{1,2}
(1 )
oocms=# SELECT '{1, 2}'::INT[];
int4
---
{1,2}
(1 )
oocms=# SELECT ARRAY[];
ERROR: syntax error at or near ] at character 14
oocms=# SELECT
Markus Bertheau wrote:
is the empty array representable in PostgreSQL, and is it
distinguishable from NULL?
Yes, and yes.
regression=# select '{}'::int[];
int4
--
{}
(1 row)
regression=# select NULL::int[];
int4
--
(1 row)
Since NULL array elements are not currently supported,
you can find more information here: http://www.postgresql.org/docs/7.4/static/sql-createtable.html (under the parameters section). For unique constraints, the only thing I can think of is a table check constraint (SELECT count(pk)=0).
I agree with you, right now there are many inconveniences
, 28.06.2004, 18:26, Joe Conway :
Markus Bertheau wrote:
is the empty array representable in PostgreSQL, and is it
distinguishable from NULL?
Yes, and yes.
Since NULL array elements are not currently supported, attempting to
construct an array with a NULL element results in NULL,
Markus Bertheau wrote:
How do I specify an empty array with the standard syntax?
Actually, up until the 7.4 release, the array literal syntax was the
*only* syntax (i.e. '{...}'). The newer array constructor expression
(i.e. ARRAY[...]) does not yet support creating empty arrays -- there
are
Markus Bertheau wrote:
How do I specify an empty array with the standard syntax?
Actually, up until the 7.4 release, the array literal syntax was the
*only* syntax (i.e. '{...}'). The newer array constructor expression
(i.e. ARRAY[...]) does not yet support creating empty arrays -- there
are
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Markus Bertheau [EMAIL PROTECTED] writes:
oocms=# SELECT ARRAY(SELECT 1 WHERE FALSE);
?column?
--
This one seems strange to me. Shouldn't it result in an empty array?
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Hi.
I'm just curious - why is it not possible to use the = operator to
compare values with NULL? I suspect that the SQL standard specified
it that way, but I can't see any ambiguity in an expression like AND
foo.bar = NULL. Is it because NULL does not equal any value, and the
expression should be
You are exactly right - the way I think about it is that if you have two
values which are unknown (a null column and NULL) it does not follow
that they are equal to each other.
As far as TRUE and FALSE go, from what I know you can use = to compare
them with boolean columns, unless I misunderstood
On June 28, 2004 03:02 pm, Stefan Weiss wrote:
I'm just curious - why is it not possible to use the = operator to
compare values with NULL? I suspect that the SQL standard specified
it that way, but I can't see any ambiguity in an expression like AND
foo.bar = NULL. Is it because NULL does not
I'm just curious - why is it not possible to use the = operator
to compare values with NULL? I suspect that the SQL standard
specified it that way, but I can't see any ambiguity in an
expression like AND foo.bar = NULL. Is it because NULL does not
equal any value, and the expression should be
Think about a join where you do something like:
t1.f1 = t2.f1
If both columns were blank, would you want the join to succeed? Probably not, if you
did, then you
would potentially have a cartesian select. This is not a good explanation of NULL
non-equality, but
I thought it might be useful.
Re,
thanks for all the replies.
On Tuesday, 29 June 2004 00:17, Dmitri Bichko wrote:
As far as TRUE and FALSE go, from what I know you can use = to compare
them with boolean columns, unless I misunderstood your question.
Sorry, I must have remembered that incorrectly, or maybe I've been
On Tue, 29 Jun 2004, Stefan Weiss wrote:
On Tuesday, 29 June 2004 00:17, Dmitri Bichko wrote:
As far as TRUE and FALSE go, from what I know you can use = to compare
them with boolean columns, unless I misunderstood your question.
Sorry, I must have remembered that incorrectly, or maybe
in my app i have a table where the id serves as a foreign key for one or more
other tables. if i want to delete a row in the table, i currently search the
other tables where this table is referenced to see if the row is in use - and
then, if not in use, permit deletion. Now if i want the delete
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