CODEWITHSUNDEEP
phpmysql
noobaroonie
noobaroonie

Reputation:

PHP mysql_query not returning false

Just learning PHP and I'm having some trouble understanding mysql_query. My understanding is that mysql_query is supposed to return FALSE if the record is not found. However, it seems that it always returns true because "FOUND!" is always the result:

$q = "SELECT * FROM users WHERE username = 'doesnotexist'";

$r = mysql_query($q);

if (!$q) {
    echo "<p>NOT FOUND!</p>";
} else {
    echo "<p>FOUND!</p>";
}

mysql_close();

Thanks in advance for any light you can shed.

Upvotes: 2

Views: 5207

Answers (6)

idontneedadisplayname
idontneedadisplayname

Reputation: 13

Ok i have worked out the answer to this.

This is the version for updating a database that tells you if a record was valid.

$updatequery = "update `mydb` set `userid` = '$arr[0]', `name` = '$arr[1]' where `age` = '$arr[2]'";

$updatequeryresult= mysql_query($updatequery);

$howmanyupdatedrecords = mysql_affected_rows();

if ($howmanyupdatedrecords == 0) {
echo("The update didn't update any records as no one matched an age of " .$arr[2]");
}

This will iterate through the DB updating all people with the specified age, if the age does not exist in the DB a message will be displayed showing you the age that does not exist. Also something to note, even if the mysql query matches a record, it won't update the record if the data already matches what it is being updated to. This causes the script to return "no one matched an age" even though there are people who did match. Can only attribute that to a bug in mysql. I told MySQL to update the information I don't see why it should take it upon itself to not bother doing as i told it. ;)

Upvotes: 1

popcornman
popcornman

Reputation: 1

if that dosen't work, try this:

<?php
$q = "SELECT * FROM users WHERE username = 'doesnotexist'";
$r = mysql_query($q);
if (!mysql_num_rows($r) >= 1) {
        echo "<p>NOT FOUND!</p>";
} else {
        echo "<p>FOUND!</p>";
}
mysql_close();
?>

Upvotes: 0

kylex
kylex

Reputation: 14406

if (empty($r)) {
        echo "<p>NOT FOUND!</p>";
} else {
        echo "<p>FOUND!</p>";
}

The following things are considered to be empty:

"" (an empty string)
0 (0 as an integer)
"0" (0 as a string)
NULL
FALSE
array() (an empty array)
var $var; (a variable declared, but without a value in a class)

Upvotes: 2

artlung
artlung

Reputation: 34013

mysql_query returns false if there is an error, not if there are no results found. From the documentation:

For SELECT, SHOW, DESCRIBE, EXPLAIN and other statements returning resultset, mysql_query() returns a resource on success, or FALSE on error.

For other type of SQL statements, INSERT, UPDATE, DELETE, DROP, etc, mysql_query() returns TRUE on success or FALSE on error.

mysql_query() will also fail and return FALSE if the user does not have permission to access the table(s) referenced by the query.

If you want to check to see if there were results returned by your query, use mysql_num_rows(). See the documentation:

Use mysql_num_rows() to find out how many rows were returned for a SELECT statement or mysql_affected_rows() to find out how many rows were affected by a DELETE, INSERT, REPLACE, or UPDATE statement.

Upvotes: 12

jerryjvl
jerryjvl

Reputation: 20121

Your 'if (!$q)' should be 'if (!$r)' I think.

Upvotes: 0

Jarod Elliott
Jarod Elliott

Reputation: 15670

You are checking the '$q' variable (your sql statement) instead of the '$r' variable (the mysql result)

Upvotes: 3

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