How to check to see if something exists, if not do this

[msaz87]

Hey All,

 

Just a quick question... I'm looking to complete an if/then statement in PHP by checking to see if there's an entry in a DB table.

 

Basically, I'm wondering how to go about making a query that says:

 

$query = " SELECT * FROM table WHERE col = '$whatimlookingfor' ";

 

So if there is no column in that table matching the variable, it would make $truefalse = '0', which could then be used later in the PHP if/then...

 

Hopefully that makes sense... any help or guidance is appreciated. Thanks!

[Mchl]

Use mysql_nym_rows to see if this query returns 0 or more rows.

[Kryptix]

Use mysql_nym_rows to see if this query returns 0 or more rows.

He means mysql_num_rows

[Mchl]

I do. You now may deduce I have a civilised QWERTY keyboard as opposed to barbaric QWERTZ or esoteric Dvorak layout.

 

Fortunately PHP manual's search yields quite good results in this case.

[msaz87]

I do. You now may deduce I have a civilised QWERTY keyboard as opposed to barbaric QWERTZ or esoteric Dvorak layout.

 

Fortunately PHP manual's search yields quite good results in this case.

 

I was able to deduce as much... this looks like it'll work perfectly -- thanks very much for all your help!

[roopurt18]

Don't use that query to see if something exists and don't use the mysql_num_rows() method.

 

The query you've presented will return the data in all of the rows.  Let's say your average record is 500 bytes.

 

Now let's say your database contains 1,000 records that meet the criteria.  You'll be returning all 1,000 records at 500 bytes per record.

 

1) This is making the database do way more work than it has to.

2) Your sending excessive data through the connection between your application and the database (500,000 bytes in my example).

 

Use something like this:

 

<?php
$escaped_variable = mysql_real_escape_string( $_POST['some_input'] );
$count_stmt = "
    SELECT COUNT(*) AS `n`
    FROM `yourtable`
    WHERE `thecol`={$escaped_variable}
    ";

$q_handle = mysql_query( $count_stmt );
$count = 0;
if( $q_handle ) {
    $count_row = mysql_fetch_object( $q_handle );
    if( $count_row ) {
        $count = $count_row->n;
    }
}
echo "There are {$count} records matching the criteria.";
?>

[Mchl]

Or just use LIMIT 1