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exceptional logic


exceptional logic

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BenWard
BenWard
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Comments posted to this topic are about the item exceptional logic

Ben

^ Thats me!


----------------------------------------
01010111011010000110000101110100 01100001 0110001101101111011011010111000001101100011001010111010001100101 01110100011010010110110101100101 011101110110000101110011011101000110010101110010
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bitbucket-25253
bitbucket-25253
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Nice question

If everything seems to be going well, you have obviously overlooked something.

Ron

Please help us, help you -before posting a question please read

Before posting a performance problem please read
Andre Guerreiro
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That looks and executes right... but I can't understand why the result is not only the number 4.

After the EXCEPT, only the number 4 remains. So where does that 5 come from in the INTERSECT part?

I'm testing it in SSMS but I don't get it. Unsure

Best regards,

Best regards,

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SQLRNNR
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Thanks



Jason AKA CirqueDeSQLeil
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SQL RNNR

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vk-kirov
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Nice question

codebyo (10/10/2011)
That looks and executes right... but I can't understand why the result is not only the number 4.

After the EXCEPT, only the number 4 remains. So where does that 5 come from in the INTERSECT part?


Please be aware that the INTERSECT operand has higher precedence than the EXCEPT and UNION operands (http://msdn.microsoft.com/en-us/library/ms188055.aspx):
EXCEPT and INTERSECT (Transact-SQL)
Remarks
If EXCEPT or INTERSECT is used together with other operators in an expression, it is evaluated in the context of the following precedence:
1. Expressions in parentheses
2. The INTERSECT operand
3. EXCEPT and UNION evaluated from left to right based on their position in the expression

So, the code given in the QOTD is equal to the following pseudocode:
( (1, 2, 5)
union
(1, 2, 4) )
except
( (1, 2, 5)
intersect
(1, 2, 4) )


Which is equal to the following pseudocode:
(1, 2, 4, 5)
except
(1, 2)


Which gives us "4, 5" as a result.
Nakul Vachhrajani
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This is a good, useful QotD. Thank-you!

Thanks & Regards,
Nakul Vachhrajani.
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palotaiarpad
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That was a nice question. But in production code i would have used paraenthesis for better readability. :-P
Carlo Romagnano
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palotaiarpad (10/11/2011)
That was a nice question. But in production code i would have used paraenthesis for better readability. :-P

Me, too! :-D

I run on tuttopodismo
MarkusB
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Very good question even though I missed the point that INTERSECT precedes EXCEPT

Markus Bohse
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Good question, thanks.

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