title: How to continue sql script on error?
body: <p>We have a couple of migration scripts, which alter the schema from version to version.</p>
  
  <p>Sometimes it happens, that a migration step (e.g. adding a column to a table) was already done manually or by a patch installation, and thus the migration script fails.</p>
  
  <p>How do I prevent the script from stopping on error (ideally at specific expected errors) and instead log a message and continue with the script?</p>
  
  <p>We use PostgresQL 9.1, both a solution for PostgresQL as well as a general SQL solution would be fine.</p>