title: How to update database table schemas with NHibernate schema generation?
body: <p>I'm trying to figure out how to use NHibernate configuration with mapping to update table schemas, rather than dropping and recreating them.</p>
  
  <p>Currently I'm using the <code>NHibernate.Tool.hbm2ddl.SchemaExport</code> obj with FluentNHibernate to generate the database schema for a mysql database.  While I can't say it's a huge problem, whenever I call <code>SchemaExport.Execute</code> on the database, it's going to drop all the tables and then recreate them.  </p>
  
  <p>What would be way cooler is if I could just have it update the existing table structures retaining data where possible.  But I don't really want to use a commerical product, or a code generator, because I don't like code generation in general, and I don't need this enough that I would consider paying for it. So hopefully any answer would keep these caveats in mind.</p>