title: Adding a new column in a temporary table
body: <p>I have a temporary table in a PostgreSQL function and I want to insert a new <code>VARCHAR</code> column. It should have a value that depends on another column of the table, named "amount". </p>
  
  <p>When the amount is positive I would like the value of the column row to be credit and when the value is negative the column should be debit.</p>
  
  <p>I have one more request: I want to round the value of amount column in 2 decimal digits</p>