使用mysql查询作为条件

Question

I have a table in a mySQL database where i put a value retrieved from an android application using php. Now the value is a UniqueID,so i am keeping a count of it,so that i can know how many times my application is accessed. When a new UniqueID arrives it is added to the database with count=1 and when an existing UniqueID is retieved,its count is simply incremented. I tried my php script multiple times but with no luck. I am attaching my php script for reference.

<?php


ini_set('default_charset', 'utf-8');
header('Content-Type: text/html; charset=UTF-8');
$n=$_POST['UniqueID'];  
$count=1;  
$Today=date("F j, Y, g:i a");

mysql_connect("localhost","root","");  
mysql_select_db("farm-o-pedia");

$con="select userid from uniqueid";  
$result=mysql_query($con) or die(mysql_error());  
if($result=$n)  
{  

$upd="update uniqueid set count=count+1 where userid=$n";  
$result=mysql_query($upd) or die(mysql_error());  
}  
else  {  
$que="insert into uniqueid (userid,count,date) values($n,\"$count\",\"$Today\")";    
$sql=mysql_query($que) or die(mysql_error());  
}

mysql_close();
?>

Any help would be appreciated.Thanks!

Answer 1

Another way of doing this is by taking advantage of MySQL's ON DUPLICATE KEY UPDATE

The first thing to do is to define a UNIQUE constraint on column userid ( if it is PRIMARY KEY then skip this step. ),

ALTER TABLE uniqueid ADD CONSTRAINT tb_uq UNIQUE (userid)

After the query has been executed, the ON DUPLICATE KEY UPDATE will work just fine now.

You will have no SELECT and other IF s on this.

INSERT INTO UNIQUEID (userID `count`, date)
VALUES ('idHere', 0, NOW())
ON DUPLICATE KEY 
UPDATE `count` = `count` + 1;

• INSERT ... ON DUPLICATE KEY UPDATE Syntax

Answer 2

mysql_query returns a resultset , not a single result, so:

$con="select userid from uniqueid";  
$result=mysql_query($con) or die(mysql_error());  
if($row=mysql_fetch_assoc($result)) { //if a row is found in resultset, then you already have this id in your table
    $upd="update uniqueid set count=count+1 where userid=$n";  
    $result=mysql_query($upd) or die(mysql_error());  
} else {  
    $que="insert into uniqueid (userid,count,date) values($n,\"$count\",\"$Today\")";    
    $sql=mysql_query($que) or die(mysql_error());  
}

Also you should start using mysqli functions instead of mysql, as mysql ones are deprecated

Answer 3

Look at the line if($result=$n) - this will never work. Partly the comparison operator is == not = also the result string consists of a query result not a single value.

Replace the line with:

if (mysql_num_rows($result)===1)  

Secondly you should really look into escaping your query and preferrably change from using deprecated mysql_* functions into PDO or mysqli.