PHP mysql查询不生成结果

Question

I have a problem with the below query not producing a result. There is nothing wrong with the query. But it is being run after a lot of other time and memory consuming instructions within a PHP script. If I restrict the number of operations performed in the script before this query is executed, it works.

How do I find out what the problem is? Is there a way to be notified if the script exceeds memory or execution time limitations? Or could there be another reason?

$query="SELECT * FROM user" or die(mysql_error());
$result=mysql_query($query);

if($result)
{
    success();
}
else //error
{
    failure();
}

Answer 1

or die(mysql_error()) should be added after the query is executed:

$query="SELECT * FROM user";
$result=mysql_query($query) or die(mysql_error());

Also, the else will never execute because you die() before that.

I suggest this:

$query="SELECT * FROM user";
$result=mysql_query($query);

if($result)
{
    success($result);
}
else //error
{
    failure(mysql_error());
}

Answer 2

You are using or with string.

$query="SELECT * FROM user";
$result=mysql_query($query);

if($result)
{
    success();
}
else //error
{
    failure();
}

Answer 3

First of all, you can always check if there is a mysql error by using mysql_error() which returns the mysql error string if it exists.

Second, to see if your query returned any rows, use mysql_num_rows($result) > 0 .