基本的MySQL查询没有结果

Question

I got a simple query looking like this:

$con = mysqli_connect("host","username","password","default_database");

if(mysqli_connect_errno($con))
{
    mysqli_connect_error();
}
else
{
    $query = "SELECT * FROM `users_t`";
    $result = mysqli_query($query) or die (mysql_error());
    while($row = mysqli_fetch_assoc($result))
    {
        echo $row['email'];
    }

}

Running this query gives me absolutely nothing. No errors but no result at the same time. I can't figure out whats wrong, help me please.

Answer 1

It looks like there may be a few things going on here:

1. According to the mysqli_connect_errno() Documentation , you should be checking for !$con rather than mysqli_connect_errno($con) in your if statement.
2. When a connection error is encountered, you're calling the error function but not printing it.
3. According to the mysqli_query() documentation , the first argument should be the database connection, the second being the query itself.
4. When a query errors out, you're calling mysql_error() when you should be calling mysqli_error() , passing it the connection. Again, according to documentation

Try this out and see if this resolves your problems:

<?php
$con = mysqli_connect("host","username","password","default_database");

if(!$con) {
  print mysqli_connect_error();
} else {
  $query = "SELECT * FROM `users_t`";
  $result = mysqli_query($con, $query) or die (mysqli_error($con));
  while($row = mysqli_fetch_assoc($result)) {
    echo $row['email'];
  }
}

Answer 2

$result = mysqli_query($query) or die (mysql_error());

Needs a mysqli resource link and also its not mysql_error()

if ($result = mysqli_query($con,$query))
{
while($row = mysqli_fetch_assoc($result))
    {
        echo $row['email'];
    } 
}

Answer 3

PHP is case-sensitive, so there is a very good change that your column in the database is actually named Email and then you have no result when you check $row['email'] , because the E has to be upper case.

What you can do is make sure you use the right case in PHP, or select just the fields you want. MYSQL isn't case-senstive, so if you do the following it will work.

Also a good way to check if you have the right case: use var_dump($row) (I've added it to the code just to show you)

$con = mysqli_connect("host","username","password","default_database");

if(mysqli_connect_errno($con))
{
    mysqli_connect_error();
}
else
{
    $query = "SELECT email FROM `users_t`";
    $result = mysqli_query($query) or die (mysql_error());
    while($row = mysqli_fetch_assoc($result))
    {
        echo $row['email'];
        var_dump($row);
    }

}