title: Unique sequence for a column in oracle table
body: <p>I am trying to load a table where i have a PK column called E_id. I want to generate a unique ID for this column every time a row is loaded into this table at informatica level. But i want this e_id column to generate a unique value at table level. Can i achieve this by writing a query to this column at table create script itself?
  Currently i tried this method of defaulting the value with this </p>
  
  <pre><code>e_id NUMBER DEFAULT TO_NUMBER(TO_CHAR(SYSTIMESTAMP, 'YYYYMMDDHH24MISSFF9')) NOT NULL
  </code></pre>
  
  <p>Although at times i am getting the same value for two records. 
  Can someone help how to go about this?</p>
  
  <p>TIA.</p>