内部加入Where子句？

$InnerJoinQuery = $STD->query("
        SELECT Users.ID, Users.Username, Users.Password, UserInformation.LastName, UserInformation.Firstname, UserInformation.DOB
        FROM Users AS Users 
        INNER JOIN UserInformation AS UserInformation 
        ON Users.ID = UserInformation.UserID WHERE Users.Username=".$_SESSION['real_name']."");
        $InnerJoinArray = $InnerJoinQuery->fetch_array(MYSQLI_ASSOC);

My Above code is causing an error. It works up to the point of my WHERE Clause.

WHERE Users.Username=".$_SESSION['real_name']."

How can i Impliment this into my innerjoin?

Update:

$InnerJoinQuery = $STD->query("
        SELECT Users.ID, Users.Username, Users.Password, UserInformation.LastName, UserInformation.Firstname, UserInformation.DOB
        FROM Users
        INNER JOIN UserInformation
        ON Users.ID = UserInformation.UserID WHERE Users.Username = '".$_SESSION['real_name']."'");
        $InnerJoinArray = $InnerJoinQuery->fetch_array(MYSQLI_ASSOC);



        $_SESSION['UID'] = $InnerJoinArray['ID'];
        $_SESSION['Password'] = $InnerJoinArray['Password'];
        $_SESSION['Firstname'] = $InnerJoinArray['Firstname'];
        $_SESSION['LastName'] = $InnerJoinArray['LastName'];
        $_SESSION['DOB'] = $InnerJoinArray['DOB'];
            print_r($_SESSION);

This returns:

Array ( [real_name] => inhumaneslayer [Password] => [UID] => [Firstname] => [LastName] => [DOB] => )

Which is not expected.

When I change my Query To:

$InnerJoinQuery = $STD->query("
        SELECT Users.ID, Users.Username, Users.Password, UserInformation.LastName, UserInformation.Firstname, UserInformation.DOB
        FROM Users
        INNER JOIN UserInformation
        ON Users.ID = UserInformation.UserID WHERE Users.Username = 'inhumaneslayer'");

I get the expected result:

Array ( [real_name] => inhumaneslayer [Password] => PASSWORDHIDDEN [UID] => 5 [Firstname] => xx [LastName] => xx [DOB] => DOBHIDDEN )

Which is expected.

I am unsetting session by unset($_SESSION); prior to changing the SQL

You have to enclose the string in quotes:

... Users.Username='".$_SESSION['real_name']."'")

Also - you need to escape the variable properly. How exactly you would do that - depends on the DB library you use. In your case it's http://php.net/manual/en/mysqli.real-escape-string.php

... Users.Username='". $STD->real_escape_string($_SESSION['real_name']) ."'")

But better - learn how to use prepared statements http://php.net/manual/en/mysqli.prepare.php

$stmt = $STD->query("
        SELECT Users.ID, Users.Username, Users.Password, UserInformation.LastName, UserInformation.Firstname, UserInformation.DOB
        FROM Users AS Users 
        INNER JOIN UserInformation AS UserInformation 
        ON Users.ID = UserInformation.UserID WHERE Users.Username=?");

$stmt->bind_param("s", $_SESSION['real_name']);

$stmt->execute();
$result = $stmt->get_result();

$InnerJoinArray = $result->fetch_array();

you're forgetting the (single/double) quote around your string (you are looking for a string, not integer?)

Try: ".... WHERE Users.Username='".$_SESSION['real_name']."'")

otherwise, the way you had it, it would search for

WHERE Users.Username=some_string (instead of Users.Username='some_string')which will return an error since some_string is a string and it needs to be wrapped in quotes

If still no results:

try putting your query in a variable $query = "SELECT Users .....";

Then echo $query and see what your $_SESSION variable is actually producing. Without knowing that, there's not much more I can do to help.