title: How can I write a SQL statement to update a column in a table from another column in the same table?
body: <p>I have an oracle DB where a program is writing into two columns when it updates the table.  The 2nd column is based on the value from the 1st column.  Well over time people have hand edited the database and forgot to insert values into the 2nd column.  I'd like to write a simple sql statement that updates all columns and syncs the 2nd column to the 1st column.  I know there's some simple statement to do this.  Doing a little googling I thought something like the following:</p>
  
  <pre><code>UPDATE suppliers 
  SET supplier_name = ( 
      SELECT customers.name 
      FROM customers 
      WHERE customers.customer_id = suppliers.supplier_id
  ) 
  WHERE EXISTS ( 
      SELECT customers.name 
      FROM customers 
      WHERE customers.customer_id = suppliers.supplier_id
  );
  </code></pre>
  
  <p>However, that is between 2 different tables where I would be doing it on the same table.</p>