Does NULL <> 'string'?

[Lost User]

Thank you for help me learning English. What such a insignifican word like "about" can change everything :laugh: Thank you Bruno

[hpcoder2]

Actually, the same sort of thing happens in floating point arithmetic, in pretty much any language under the sun. The values NaN (yes, there's more than one type of NaN) always return false when compared with any other number. So both NaN==x and NaN != x are false. etc., etc. This has bitten me in the arse a number of times, and I work in C++.

[Lost User]

Chris Maunder wrote:

to get the correct result.

The other result was also correct, just not the one you wanted. The behaviour is logical. Your last example would be very VB-ish, where a "NULL" value is treated like an empty string. In the database-world, an empty value does not mean an empty string. ..and it is not something recent, is it? :p

Bastard Programmer from Hell :suss: If you can't read my code, try converting it here[^][](X-Clacks-Overhead: GNU Terry Pratchett)

[Chris Maunder]

Eddy Vluggen wrote:

The other result was also correct, just not the one you wanted

This is exactly why I love programming.

cheers Chris Maunder

[TheGreatAndPowerfulOz]

It's also not the lounge.

#SupportHeForShe Government can give you nothing but what it takes from somebody else. A government big enough to give you everything you want is big enough to take everything you've got, including your freedom.-Ezra Taft Benson You must accept 1 of 2 basic premises: Either we are alone in the universe or we are not alone. Either way, the implications are staggering!-Wernher von Braun

[TheGreatAndPowerfulOz]

My sarcasm meter just broke.

#SupportHeForShe Government can give you nothing but what it takes from somebody else. A government big enough to give you everything you want is big enough to take everything you've got, including your freedom.-Ezra Taft Benson You must accept 1 of 2 basic premises: Either we are alone in the universe or we are not alone. Either way, the implications are staggering!-Wernher von Braun

[Rob Grainger]

Exactly - in Codd's original work (which defined Relational Database Management Systems), this is referred to as null progagation. Interesting, in The Relational Model for Database Management Systems V2, he introduced two null values one indicates the value is unknown and inapplicable (like the null behaviour you described), and the other indicating the value is unknown and applicable (which would give the behaviour Chris was expecting). Sadly, to the best of my knowledge, no-one bothered pursuing any of the good ideas in there.

"If you don't fail at least 90 percent of the time, you're not aiming high enough." Alan Kay.

[Rob Grainger]

I prefer the idiom...

(TableTwo.StringColumn <> 'value') or TableTwo.StringColumn is null

I find it a bit more readable (never really liked the name of the IsNull function).

"If you don't fail at least 90 percent of the time, you're not aiming high enough." Alan Kay.

[Lost User]

In the end I can feel with you. I just entered the trap with NULL values _one more again_ :^) :-D SELECT xyz FROM Tbl1 LEFT JOIN Tbl2 ON Tbl2.Tbl1_ID = Tbl1.ID WHERE Tbl1.IntValue <> Tbl2.IntValue Where in both tables NULL Values are allowed for the field IntValue. S*t happens :doh:

[al3c]

It's either col equals null meaning a field with no value or you've got an epmty string you can use

Select *
From Table
Where (col is null or col = '')

or IsNull method to find epty strngs and null values _______________________________________________________________________________________________ Alec programming[^] expert