On Sat, 28 Mar 2009 09:42:59 +0000, Dermot
<paik...@googlemail.com> wrote:
>2009/3/28 Jay A. Kreibich <j...@kreibi.ch>:
>> On Fri, Mar 27, 2009 at 05:37:49PM +0000, Dermot scratched on the wall:
>>
>>> The statement is:
>>>
>>> SELECT COUNT(*) FROM products WHERE productid=808800033 AND
>>> (allowcountry2 & 0x0000000000000001)
>>> SELECT COUNT(*) FROM products WHERE productid=808800033 AND
>>> (allowcountry1 & 0x8000000000000000)
>>>
>>> I believe the allowcountry part is a bit pattern lookup but I can't
>>> find a definition for the & and so I am not sure what the statement
>>> does bar count the results.
>>
>> To actually answer your question, yes, "&" in SQLite and some other
>> DBs is a bitwise "and" operator, just like the C/C++ "&" operator.
>> "|" is a bitwise "or".
>>
>> It is my understanding that these operators are not part of the
>> SQL standard, but a number of databases implement the operator.
>
>First off, sorry it was such an off-topic question. Thank you Jay for
>the answer.
>
>I can't find any reference to the ampersand's usage in my new book, my
>copy of learning MySQL or the SQLite Syntax documentation. I would
>have expected symbols to be listed before A in the index myself. There
>are references to bitmap indices. Symbols refer to the BNF notation
>but without reference to &. I have posted to SQLQueries. Hopefully I
>can get an understanding of what that statement means from there.
For future reference, here's an explanation of all binary
operators, that is the
-> [expr] -> (binary-operator) -> [expr] ->
part of the expr BNF diagram on
http://www.sqlite.org/lang_expr.html
A few of those are bitwise.
pre-
ce-
den- opera-
ce tor operation
---- ------ ---------------
1 || concatenation
2 * multiplication
2 / division
2 % modulo (remainder of integer division)
3 + addition
3 - subtraction
4 << bitwise shift left
4 >> bitwise shift right
4 & bitwise AND
4 | bitwise OR
5 < less than
5 <= less than or equal
5 > greater than
5 >= greater than or equal
6 = equal
6 == equal
6 != not equal
6 <> not equal
6 IN subset of
6 LIKE case insensitive equality
with % and _ wildcards
6 GLOB case sensitive equality
with Unix style file globbing syntax
6 MATCH reserved for user C function match()
6 REGEXP reserved for user C function regexp()
7 AND boolean (logical) AND
8 OR boolean (logical) OR
(Note to the SQLite developers: I could put this in the wiki
but it might be better to update the
http://www.sqlite.org/lang_expr.html#binaryops page itself)
> Again sorry for the post.
No problem.
>Dp.
--
( Kees Nuyt
)
c[_]
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