Re: Issue with NULL varchars

[Craig Ringer <craig(at)postnewspapers(dot)com(dot)au>]

antony baxter wrote:

>       // Retrieve that Locale's ID by its Data:
>       p = c.prepareStatement("SELECT COUNT(*) FROM testing WHERE variant = ?");

To avoid conditionally rewriting your query to use IS NULL / IS NOT NULL
instead of equality, you could also use IS DISTINCT FROM. Instead of:

	where variant = ?

try using:

	where not (variant is distinct from ?)


craig=# \pset null '<null>'
Null display is "<null>".

craig=# select null = null;
 ?column?
----------
 <null>
(1 row)

craig=# select not( null is distinct from null );
 ?column?
----------
 t
(1 row)

craig=# select not (1 is distinct from 1);
 ?column?
----------
 t
(1 row)

craig=# select not (1 is distinct from 2);
 ?column?
----------
 f
(1 row)

craig=# select not (null is distinct from 2);
 ?column?
----------
 f
(1 row)


See:

http://www.postgresql.org/docs/8.3/static/functions-comparison.html

--
Craig Ringer