How i can checking the duplicate links with php and mysql ??

mikhak

i have a database like this :

database name : link

id username linkterm linkurl

1 a google google.com

2 a yahoo yahoo.com

3 c google2 google.com

4 d ask ask.com

i want checking the duplicate links when my user want adding new link . for example if my user want adding the google.com my php codes should printing a error that this link is duplicate links. i have to google.com links in my database i don't have any problem this item but i want don't have any other google.com in " a " user .

i wrote this code but not working :

$oldlink = mysql_query("SELECT COUNT(linkurl) FROM `link` where `username`=a AND `linkurl`=google.com");
if($oldlink>0){
echo 'duplicate links';
}
else{
echo 'links submitted';
}

please help me .

thank you.

schwim

Try this one on for size:

$oldlink = mysql_query("SELECT COUNT(id) AS id FROM link WHERE username = 'a' AND linkurl = 'google.com'");
$olnum = mysql_fetch_array($oldlink);
if($olnum["id"] != 0){
	/* Duplicate record */
}else{
	/* No record found */
}

I think that should work for you.

laserlight

schwim's suggestion is likely to work, but it leaves open the small chance that the user could somehow add the same link twice because of say, a repeated form submission, such that the checks for the existing linkurl happen just before the insertions.

To avoid this, one approach is to create a unique constraint on the username and linkurl. Then, instead of doing a select before the insertion, you can just insert, then handle the unique constraint violation, if any.

mikhak

schwim;11046099 wrote:

Try this one on for size:

$oldlink = mysql_query("SELECT COUNT(id) AS id FROM link WHERE username = 'a' AND linkurl = 'google.com'");
$olnum = mysql_fetch_array($oldlink);
if($olnum["id"] != 0){
	/* Duplicate record */
}else{
	/* No record found */
}

I think that should work for you.

thank you my problem is solved. very very thanks.

NogDog

{EDIT: Heh...couple replies came in while I was typing this up and finding a link. 🙂 }

If it's a hard limit, then the database table should have a unique index across the user id column and the link column (term or url or both?). Then when you try to insert a new link, the query will fail, and if you trap the DB error code*, you can tell if it was because of unique key constraint, in which case you output the error message to the user. (If it's some other error code, then you have a more serious problem you'll need to perhaps log debug info for and let the user know it was a more generic failure that you'll be looking into.)

1022 in MySQL