>>>>> Simon Slavin writes:
>>>>> On 9 Oct 2011, at 3:57am, 张一帆 wrote:
>> i have some data like "a and b or c ...",there will be a word 'and'
>> or 'or' which means the Logical relations between each item.
> If you have "a and b or c" does that mean
> (a and b) or c OR
> a and (b or c) ?
> How does your software know ?
The boolean AND and OR operations are often compared to the
usual arithmetics' × and +. Therefore, a AND b OR c is akin to
a × b + c, and the precedence rules (borrowed from arithmetics)
will make that (a × b) + c.
And SQLite, among many others, behaves just like that:
$ sqlite3 :memory: 'SELECT 0 AND 1 OR 1'
1
$ sqlite3 :memory: 'SELECT 0 AND (1 OR 1)'
0
$
I guess that it just follows the standard.
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