Does NULL <> 'string'?
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Au contraire. It's the perfect language. Job security forever.
cheers Chris Maunder
Quote:
Job security forever
Indeed. Writing script, backup,... It's boring but secure.
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Quote:
Job security forever
Indeed. Writing script, backup,... It's boring but secure.
So is prostitution... but ya know... :~
Jeremy Falcon
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I think this version reads cleaner (and without the quirks), but I'd be willing to bet the non-sub select version would run quicker.
Jeremy Falcon
Assuming SQL Server, I'll take that bet. NOT IN vs. NOT EXISTS vs. LEFT JOIN / IS NULL: SQL Server at EXPLAIN EXTENDED[^] Left outer join vs NOT EXISTS | SQL in the Wild[^] There are always exceptions, but
not existsis generally better optimized.Wrong is evil and must be defeated. - Jeff Ello
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Null most certainly does not equal a valid string value, right? I never realised SQL could be so Javaesque ;)
cheers Chris Maunder
It gets Dali-esque as well from time to time...
Bad command or file name. Bad, bad command! Sit! Stay! Staaaay... AntiTwitter: @DalekDave is now a follower!
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So is prostitution... but ya know... :~
Jeremy Falcon
Boring?
Wrong is evil and must be defeated. - Jeff Ello
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Boring?
Wrong is evil and must be defeated. - Jeff Ello
Some are... so I'm told. :rolleyes:
Jeremy Falcon
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Boring?
Wrong is evil and must be defeated. - Jeff Ello
They don't all "enjoy" it. It's a job. Indeed, prostitutes go same-sex for their personal one-on-ones because opposite-sex has lost all appeal due to the "job".
#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
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So is prostitution... but ya know... :~
Jeremy Falcon
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So wait, you're saying I can't be a prostitute? Why? Because I'm a guy? That's discrimination.
Jeremy Falcon
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So wait, you're saying I can't be a prostitute? Why? Because I'm a guy? That's discrimination.
Jeremy Falcon
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Yes. Everyone knows you have go through prostitute training to get certified. You just finding this out? You may wanna talk to your MS rep.
Jeremy Falcon
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It gets Dali-esque as well from time to time...
Bad command or file name. Bad, bad command! Sit! Stay! Staaaay... AntiTwitter: @DalekDave is now a follower!
OriginalGriff wrote:
Dali-esque
Surrealistic? or womenizer? :laugh: :laugh: :laugh: :laugh:
M.D.V. ;) If something has a solution... Why do we have to worry about?. If it has no solution... For what reason do we have to worry about? Help me to understand what I'm saying, and I'll explain it better to you Rating helpful answers is nice, but saying thanks can be even nicer.
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Yes. Everyone knows you have go through prostitute training to get certified. You just finding this out? You may wanna talk to your MS rep.
Jeremy Falcon
Guys... this is not the soapbox
M.D.V. ;) If something has a solution... Why do we have to worry about?. If it has no solution... For what reason do we have to worry about? Help me to understand what I'm saying, and I'll explain it better to you Rating helpful answers is nice, but saying thanks can be even nicer.
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You'd think so. Except in SQL We had a query:
Select count(*)
From TableOnewhich returned, say, 500,000 records. Next we added
Select count(*)
From TableOne
Left Join TableTwo On TableTwo.TableTwoID = TableOne.TableTwoID
Where TableTwo.TableTwoID is null or TableTwo.StringColumn <> 'value'We're trying to find the number of records in
TableOnewhich, when joined withTableTwo, either have no corresponding TableTwo row or the correspondingTableTworow is not 'value'.TableTwo.StringColumnis nullable. The result? Adding the join resulted in 25K records. It should have been over 490K records. The issue?TableTwo.StringColumn <> 'value'
This comparison returns false if
TableTwo.StringColumnis null. So one needs to useIsNull(TableTwo.StringColumn, '') <> 'value'
to get the correct result.
cheers Chris Maunder
Like everything else in programming, it depends. In this case it depends on the SQL ansi_nulls setting. If this is a statement inside a SQL stored procedure, view, etc the ansi_nulls setting is burned into the object when it is created. If this is an ad-hoc statement then the ansi_nulls setting in effect for the SQL connection the statement is executed against is used. If you want null <> 'value' to return true, you could just set ansi_nulls off. Not that I would recommend doing that...
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Like everything else in programming, it depends. In this case it depends on the SQL ansi_nulls setting. If this is a statement inside a SQL stored procedure, view, etc the ansi_nulls setting is burned into the object when it is created. If this is an ad-hoc statement then the ansi_nulls setting in effect for the SQL connection the statement is executed against is used. If you want null <> 'value' to return true, you could just set ansi_nulls off. Not that I would recommend doing that...
txmrm wrote:
Not that I would recommend doing that...
Especially as it's deprecated, and likely to be removed:
SET ANSI_NULLS (Transact-SQL) | Microsoft Docs[^]:
In a future version of SQL Server, ANSI_NULLS will always be ON and any applications that explicitly set the option to OFF will generate an error. Avoid using this feature in new development work, and plan to modify applications that currently use this feature.
"These people looked deep within my soul and assigned me a number based on the order in which I joined." - Homer
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You'd think so. Except in SQL We had a query:
Select count(*)
From TableOnewhich returned, say, 500,000 records. Next we added
Select count(*)
From TableOne
Left Join TableTwo On TableTwo.TableTwoID = TableOne.TableTwoID
Where TableTwo.TableTwoID is null or TableTwo.StringColumn <> 'value'We're trying to find the number of records in
TableOnewhich, when joined withTableTwo, either have no corresponding TableTwo row or the correspondingTableTworow is not 'value'.TableTwo.StringColumnis nullable. The result? Adding the join resulted in 25K records. It should have been over 490K records. The issue?TableTwo.StringColumn <> 'value'
This comparison returns false if
TableTwo.StringColumnis null. So one needs to useIsNull(TableTwo.StringColumn, '') <> 'value'
to get the correct result.
cheers Chris Maunder
It may be weird, but it's nothing new... I learned SQL on mainframe, and the first thing we had to memorize about NULL is that it can not stand of either side of any of the comparison operators (=, <, >, <>)...
Skipper: We'll fix it. Alex: Fix it? How you gonna fix this? Skipper: Grit, spit and a whole lotta duct tape.
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You'd think so. Except in SQL We had a query:
Select count(*)
From TableOnewhich returned, say, 500,000 records. Next we added
Select count(*)
From TableOne
Left Join TableTwo On TableTwo.TableTwoID = TableOne.TableTwoID
Where TableTwo.TableTwoID is null or TableTwo.StringColumn <> 'value'We're trying to find the number of records in
TableOnewhich, when joined withTableTwo, either have no corresponding TableTwo row or the correspondingTableTworow is not 'value'.TableTwo.StringColumnis nullable. The result? Adding the join resulted in 25K records. It should have been over 490K records. The issue?TableTwo.StringColumn <> 'value'
This comparison returns false if
TableTwo.StringColumnis null. So one needs to useIsNull(TableTwo.StringColumn, '') <> 'value'
to get the correct result.
cheers Chris Maunder
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You'd think so. Except in SQL We had a query:
Select count(*)
From TableOnewhich returned, say, 500,000 records. Next we added
Select count(*)
From TableOne
Left Join TableTwo On TableTwo.TableTwoID = TableOne.TableTwoID
Where TableTwo.TableTwoID is null or TableTwo.StringColumn <> 'value'We're trying to find the number of records in
TableOnewhich, when joined withTableTwo, either have no corresponding TableTwo row or the correspondingTableTworow is not 'value'.TableTwo.StringColumnis nullable. The result? Adding the join resulted in 25K records. It should have been over 490K records. The issue?TableTwo.StringColumn <> 'value'
This comparison returns false if
TableTwo.StringColumnis null. So one needs to useIsNull(TableTwo.StringColumn, '') <> 'value'
to get the correct result.
cheers Chris Maunder
Total guess here, but I wonder if the SQL engine errors on the side of caution. Something like: "I don't have a string to compare to. Thus, I can't say with certainty it is or is not 'value', so I'll return false." But yeah, I think that has gotten us all at one time or another when doing inequality in a query. I also wonder if it varies with different implementations of SQL. But not enough to, you know, test it or anything.
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Yes, and it is pretty correct. NULL is not defined and can therefore not be compared to a value. Also not for nuallable type in c#.
...except there's an "or" in there: logically, it shouldn't matter: if it's null, at least one of the conditions is true. I have a feeling that "null=string" evaluates to null, and then "field is null" evaluates to Boolean, then "boolean or null" evaluates to null, which is why it doesn't work. But that's somewhat abstruse. Which server is this: is it SQL Server or MySQL... or perhaps something else?
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...except there's an "or" in there: logically, it shouldn't matter: if it's null, at least one of the conditions is true. I have a feeling that "null=string" evaluates to null, and then "field is null" evaluates to Boolean, then "boolean or null" evaluates to null, which is why it doesn't work. But that's somewhat abstruse. Which server is this: is it SQL Server or MySQL... or perhaps something else?
