title: Liquibase changelog without MD5SUM
body: <p>I have a database here which is updated using Liquibase. If I understand correctly, Liquibase will apply a changeset and write a line to the <code>DATABASECHANGELOG</code> table with the execution date and an MD5 checksum. This way, Liquibase can find out when a changeset (unexpectedly) changes.</p>
  
  <p>However, in this database, many (most) of the <code>MD5SUM</code> entries are <code>NULL</code>. I have no idea why that should be the case. Is this in any way a normal mode of operation?</p>
  
  <p>When using the Liquibase <code>status</code> command, I see many <em>‘unapplied’</em> changes. How can Liquibase determine that without the MD5 sum? Or are changesets without MD5 sums considered changed.</p>