Hi,
MySQL 5.0.41 and Postgresql 8.2.5 work as you described in their
treatment of NULL. There were some minor syntax tweaks for CREATE TABLE
and the second SELECT EXISTS, but other than that it was true for the
first SELECT EXISTS and false for the second SELECT EXISTS.
Regards,
Eugene Wee
[EMAIL PROTECTED] wrote:
The current behavior of SQLite is to not do anything special
with NULLs in an EXISTS operator. For example:
CREATE TABLE t1(x);
INSERT INTO t1 VALUES(NULL);
SELECT EXISTS(SELECT x FROM t1);
The final SELECT above returns 1 (true) because an entry exists
in t1, even though that entry is NULL. This makes logical sense
because if you wanted to know if there were non-null entries
you would say:
SELECT EXISTS(SELECT x FROM t1 WHERE x NOT NULL);
But I have long ago learned that NULL values in SQL rarely
make logical sense, so I figure I better check.
Can somebody please confirm that this is the correct behavior
and that EXISTS does not do any special treatment of NULL
values? Can somebody tell me what MySQL, PostgreSQL, Oracle,
and Firebird do in this case?
--
D. Richard Hipp <[EMAIL PROTECTED]>
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