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simple mysql question..plz answer :)

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jakx12

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simple mysql question..plz answer :)

Feb 28th, 2009

Ok so what i'd like to know is how to have two where statements in a mysql delete query. I get an error if i do this:

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mysql_query("DELETE FROM user_notifications WHERE username='$acc' AND WHERE notification='$note2'")  
or die(mysql_error());

Any help would be much appreciated, I know this is a silly question, but i havnt done any php programming for a couple of months and need to get back into it!

Thanks,

jakx12

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rickya100

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Re: simple mysql question..plz answer :)

Feb 28th, 2009

Hi,

Don't think you need the second WHERE, just the AND.

Test it out.

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jakx12

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Re: simple mysql question..plz answer :)

Feb 28th, 2009

tested it out but, it does not delete anything from the database

but there is no error

. So whats wrong?

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Re: simple mysql question..plz answer :)

Feb 28th, 2009

mysql_query("DELETE FROM user_notifications WHERE username='".$acc."' AND notification='".$note2."' ");

that should be fine. if its not, try checking your $acc and $note2 variables...

Last edited by peter_budo; Mar 1st, 2009 at 6:27 am. Reason: Keep It Organized - For easy readability, always wrap programming code within posts in [code] (code blocks) and [icode] (inline code) tags.

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Re: simple mysql question..plz answer :)

Mar 2nd, 2009

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Originally Posted by MaxMumford

mysql_query("DELETE FROM user_notifications WHERE username='".$acc."' AND notification='".$note2."' ");

that should be fine. if its not, try checking your $acc and $note2 variables...

You also need to escape the variables like this:

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mysql_query("DELETE FROM `user_notifications` WHERE `username`='".mysql_real_escape_string($acc)."' AND `notification`='".mysql_real_escape_string($note2)."' ") or die(mysql_error());
mysql_query("DELETE FROM `user_notifications` WHERE `username`='".mysql_real_escape_string($acc)."' AND `notification`='".mysql_real_escape_string($note2)."' ") or die(mysql_error());

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Re: simple mysql question..plz answer :)

Mar 2nd, 2009

To be a better php programmer always use single quotes like this,

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mysql_query('DELETE FROM user_notifications WHERE username="'.mysql_real_escape_string($acc).'" AND notification="'.mysql_real_escape_string($note2).'"') 
or die(mysql_error());
mysql_query('DELETE FROM user_notifications WHERE username="'.mysql_real_escape_string($acc).'" AND notification="'.mysql_real_escape_string($note2).'"') 
or die(mysql_error());

bcoz: php parser will search and parse full string while using double quotes.

- might look simple - but usefull tip(i think so)

Last edited by peter_budo; Mar 8th, 2009 at 6:41 am. Reason: Keep It Organized - For easy readability, always wrap programming code within posts in [code] (code blocks) and [icode] (inline code) tags.

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Re: simple mysql question..plz answer :)

Mar 2nd, 2009

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Originally Posted by vinothkumarc

To be a better php programmer always use single quotes like this,
mysql_query('DELETE FROM user_notifications WHERE username="'.mysql_real_escape_string($acc).'" AND notification="'.mysql_real_escape_string($note2).'"')
or die(mysql_error());
bcoz: php parser will search and parse full string while using double quotes. - might look simple - but usefull tip(i think so)

From what I have read in the past that is only a c++ thing. In c++ single quotes represent a single character where as with php, single quotes simply just doesn't apply new lines or returns (eg \n\r). Instead it will just display them as their literal characters. Where as double quotes in php allow those returns to be displayed instead of their literal characters. So you may find with your method that your returns will not turn out!!!

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Re: simple mysql question..plz answer :)

Mar 2nd, 2009

while using double quotes.. parser will search for php variable("my name is vinoth" instead use 'my name is vinoth') inside that string...(execution/parsing time will be greater). If we want to display the string with out any php variable('my name is '.$name)... then better to use single quotes...
its truth.... in PHP (I may not know about other languages)

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Re: simple mysql question..plz answer :)

Mar 3rd, 2009

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Originally Posted by vinothkumarc

while using double quotes.. parser will search for php variable("my name is vinoth" instead use 'my name is vinoth') inside that string...(execution/parsing time will be greater). If we want to display the string with out any php variable('my name is '.$name)... then better to use single quotes...
its truth.... in PHP (I may not know about other languages)

I can understand that when assigning a value to a variable/array that would be true but would it be the same with a mysql query. An example is the following:

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$var="line1\nline2";
mysql_query('INSERT INTO `table` SET `column`="'.$var.'"');
$var="line1\nline2";
mysql_query('INSERT INTO `table` SET `column`="'.$var.'"');

Would that record the following:

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line1
line2

Sort of a tricky thing when mixing two syntaxs together because you are unsure which syntax will be the one that will take place.

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Re: simple mysql question..plz answer :)

#10

Mar 3rd, 2009

ya ofcourse...
before executing the query.... the parser will parse the arguement... after that only the mysql_query function will execute the query...

Thanks & Regards,
VinothKumar C
post2vinoth@gmail.com