Strange phenomenon of the Access database Update statement
Source: Internet
Author: User
When I write an Update query on Access today, I accidentally
Update employee set status = 1, name = 'sind' where id = 99
Write
Update employee set status = 1 and name = 'sind' where id = 99
Result The status field is updated to 0,
I was surprised. How could it be 0? I am not very familiar with Access.
Called a colleague. He looked at it and said "Access" Regards and name = 'sind' as a Boolean statement,
After discussion, I wrote down my understanding:
Brackets are added here for your understanding.
Update employee set status = (1 and (name = 'sink') where id = 99
Because the name in the row with id 99 is not equal to 'sinsink', the result of name = 'sink' is false,
True is interpreted as-1 or 1 () by access (),
(Or-1 or 1 is equivalent to true here ),
False is equivalent to 0 (may be related to C ),
So the result of (name = 'sink') is false,
1 and false are equivalent to true and flase,
So the result is false. If it is converted into Int, It is 0, and then it is updated to 0,
The and character is converted into a logical operator.
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