title: A question about updating a table through PhpMyAdmin
body: <p>I am a database beginner, I met a problem during my study.</p>
  
  <p>I am now going to update one table of my database by importing a text file through phpMyAdmin.
  Everything worked great except for handling with rows that has same customer_ID.</p>
  
  <p>The row has a field called "customer_ID", and I cannot make this a primary key, since the initial text file used to populate the database contains multiple rows for a single customer_ID, so database must allow multiple rows for one user id.</p>
  
  <p>I populated the database with the import text file, no error. However, now I need to update the database with an update text file, the customer_id within the update text file are all already existed(populated) in the database, so if I update the database with this updated text file(through the "import" function in PhpMyAdmin), the existing rows with the same customer_ID will not be updated, but another row with the same customer_ID will be created, which is not exactly what I want.</p>
  
  <p>I think this is a dilemma, if I could make the customer_id a primary key, the update process will work perfectly, but since I need to allow customer_id appearing in multiple rows in the database populating process, so I couldn't make customer_id a primary key.</p>
  
  <p>Please pardon for the trivial question.I wonder if experts could give me some suggestion or some related readings? Thanks in advance for the help.</p>