Thanks for the reply. The parentheses are noted.
Meantime, I did some reading and came up with this ->
SELECT sc.col1 FROM search s, search_content sc WHERE s.word IN
('apache', 'mysql') AND s.wid = sc.wid
Thanks for the tip.
DL Neil wrote:
>Gerard,
>
>
>
>>Im looking for another opinion on an sql statement.
>>SELECT sc.col1 FROM search s, search_content sc WHERE s.word = 'mysql' >
>>
>>
>AND s.wid = sc.wid OR s.word = 'apache' AND s.wid = sc.wid;
>
>
>>I had to use "s.wid = sc.wid" twice in the sql for the query to work
>>properly. Is this the legal, correct way to do so.
>>
>>
>
>
>You're perfectly legal, but have become tangled up in the rules of operator
>precedence. In fact MySQL's optimiser probably takes care of it all for you.
>
>Precedence says that if there are multiple operators they will be executed
>from left to right, unless one is considered more important than the other,
>eg * precedes +, or in your case, AND precedes OR.
>
>To override precedence, or merely to help with readability, one may employ
>parentheses - calculations within parentheses are performed first. Thus the
>code becomes:
>
>WHERE ( s.word = 'mysql' AND s.wid = sc.wid )
> OR ( s.word = 'apache' AND s.wid = sc.wid );
>
>Now one can apply Boolean algebra and rationalise the apparent duplication:
>
>WHERE s.wid = sc.wid
> AND ( s.word = 'mysql' OR s.word = 'apache' );
>
>As to which is 'right' and which 'wrong', let me ask: which one do you find
>most readable?
>
>Regards,
>=dn
>
>
>
>
--
Gerard Samuel
http://www.trini0.org:81/
http://dev.trini0.org:81/
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