>>>>> "Bob" == Bob Kline <bkline@stripped> writes:
Bob> On Mon, 20 Sep 1999, Bryan Porter wrote:
>> In version MySQLd version 3.22.25, it would appear that a bug has shown
>> itself.
>>
>> To duplicate :
>>
>> Send a SQL statement equivalant to the following :
>>
>> "SELECT * FROM tblTemp WHERE tempfield = 1 AND tempfield = 0";
>>
>> 'tempfield' should never equal both 1 AND 0 in any given row. This is an
>> impossibility. However, in the version mentioned above, this query does
>> not generate an error, and happily ignores this syntax problem. Given
>> the fact that the programmer would probably have meant something else,
>> strict syntax checking should be added for this kind of SQL statement
>> (and others).
>>
>> While this is probably against the Perl idiom ("Perl thinks you should
>> stay out of it's living room because you weren't invited, not because it
>> has a shotgun") it's probably best to make MySQL complain on this and
>> other like errors, if only because they would be difficult to track
>> down.
>>
>> This is just my opinion : I apologize if the subject of this message was
>> misleading.
Bob> My opinion:
Bob> 1. This is perfectly legal SQL.
Bob> 2. It represents only the easiest case of a wide spectrum of
Bob> conditions increasingly more difficult to detect (particularly
Bob> true when MySQL supports nested queries).
Bob> One of the reasons we enjoy such blazing speed with MySQL is the fact
Bob> that the designers have deliberately chosen to leave out many of the
Bob> fancier options thrown in by most other vendors. I would assume that in
Bob> the unlikely event MySQL was modified to include checking for such
Bob> conditions:
Bob> a. they would include an option to turn the checking off; and
Bob> b. "off" would be the default.
Bob> One aspect of your post which isn't a matter of opinion: the case you
Bob> cite represents a question of semantics, not a "syntax problem"; the
Bob> query is syntactically correct.
Hi!
Just a quick note.
MySQL does detect the above case and returns at once with an empty
set (This is the only thing a SQL server is allowed to do).
To verify this you can do:
mysql> explain select * from test where id=1 and id=2;
+------------------+
| Comment |
+------------------+
| Impossible WHERE |
+------------------+
1 row in set (0.00 sec)
Regards,
Monty
