Sql Insert into with duplicate key Ok so, I'm still a beginner in databases. I have this code: 

$sql="
  INSERT INTO complaints_members
    (password, complaint) 
  VALUES 
    ('$mypassword','$submit') 
  ON DUPLICATE KEY UPDATE 
    complaint='$submit' ; 
";


This simply updates my complaint in the existing entry. How can I insert a new entry with the same key, instead of updating the old one?

I'm not very familiar with the terms of SQL, so I'm sorry in advance.
Your SQL statement specifies the behavior you are seeing with ON DUPLICATE KEY UPDATE. This syntax is shorthand for logic that causes an insert only if the key does not exist, and an update of the row identified by that key if it does exist. See the MySQL documentation for more info.

Since ON DUPLICATE KEY UPDATE only operates on primary keys or unique indexes, you cannot insert another row with the same key anyway. If multiple records with the same identifier are required in the table, you must make that identifier something other than the primary key or remove the unique constraint on the index.