title: Autoincrement of primary key column with varchar datatype in it
body: <pre><code>CREATE TABLE Persons
  (
      P_Id varchar(6) NOT NULL,
      LastName varchar(255) NOT NULL,
      FirstName varchar(255),
      PRIMARY KEY (P_Id)
  )
  </code></pre>
  
  <p>in this table <code>P_Id</code> is the primary key. We want to generate autoincrement of <code>P_Id</code> with default value (PN00) in the start while inserting only LastName and FirstName .eg :-PN001 for first entry ,PN002 for second,PN003 for third and so on .</p>