Unknown column 'unknown' in 'where clause'

Question

When the user is logged in I am trying to find their information so I can display it to them, then I am going to allow them to update their information.

I keep getting an unknown column error, which is my session variable in the where clause but I am not sure why. The code below shows my query that I am using.

$query="SELECT * FROM users WHERE username = ". $_SESSION['login_user'];

Answer 1

Best way is to use a Prepared Statement with a placeholder for the login in your SQL and replace it with the value from the Session.

Another non-production-standard way is to enclose the login value in single quotes. Without the quotes, the SQL engine is thinking the login to be a column name.

Answer 2

如果您的列username是键入的字符串，则应添加'进行过滤，如下所示：

$query="SELECT * FROM users WHERE username = '". $_SESSION['login_user'] + "'";