php - Use of ' in SQL statement -

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i doing php; found following code works

function get_total_urls() {         $total = mysql_query('select count(`url_key`) `urls`');     return (int)mysql_result($total, 0); } get_total_urls();

but following code shows warning

function get_total_urls() {         $total = mysql_query("select count('url_key') 'urls'");     return (int)mysql_result($total, 0); } get_total_urls();

shows following warning:

warning: mysql_num_rows() expects parameter 1 resource, boolean given.

please help; why 2nd code shows warning 1st code ok? 2nd code fails count of 'url_key' database table.

is there anyway write first code without back-tick , work perfectly?

this statement:

$total = mysql_query('select count(`url_key`) `urls`');

in mysql, backticks used delimit identifiers -- when conflict reserved words or contain unseemly characters (such spaces, periods, commas, , on). because idea have identifiers not conflict reserved words , contain no unseemly characters, backticks needed.

you can write:

$total = mysql_query('select count(url_key) urls');

single quotes should only used string , date constants. not use them identifiers, lead confusion. have no doubt noticed.


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