MySQLi UPDATE where子句不起作用

Question

I wrote code that is suposed to update the "user level" stored in the column "level" in the table "users", for the user specified by the variable "$x5_input_username".

$x_changelvl_sql = "UPDATE users SET level='$x5_input_newlevel' WHERE `username`=$x5_input_username";

When I do this using the userlevel "2" and username "TestUser" (which both exist in the database), it gives me this error:

Error updating record: Unknown column 'TestUser' in 'where clause'

Answer 1

Quote your string in the where clause

$x_changelvl_sql = "UPDATE users 
    SET level='$x5_input_newlevel' 
    WHERE `username`='$x5_input_username'";

Better yet, start using MySQLi with prepared statements and bind variables