title: sqlite add column if not exist with just sql
body: <p>out of curiosity is it possible to write an alter table add col statment with just sql. Since the statement is going into a script and I can't really do any sort of checks with C++.</p>
  
  <p>So pretty much I am wondering if its possible to do something in the line of</p>
  
  <p>Alter table "test" add "test_col" if 0 &lt; ( select count("test_col") from "test");
  or with combination of other sql statements.</p>
  
  <p>Thanks.</p>