title: How to work with liquibase, a concrete example
body: <p>Following the quickstart on <a href="http://www.liquibase.org/quickstart" rel="noreferrer">liquibase</a> i've created a changeset (very dumb :) )</p>
  
  <p>Code:</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="UTF-8"?&gt;
  
  &lt;databaseChangeLog
    xmlns="http://www.liquibase.org/xml/ns/dbchangelog/1.6"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://www.liquibase.org/xml/ns/dbchangelog/1.6
           http://www.liquibase.org/xml/ns/dbchangelog/dbchangelog-1.6.xsd"&gt;
  
      &lt;changeSet id="1" author="me"&gt;
          &lt;createTable tableName="first_table"&gt;
              &lt;column name="id" type="int"&gt;
                  &lt;constraints primaryKey="true" nullable="false"/&gt;
              &lt;/column&gt;
              &lt;column name="name" type="varchar(50)"&gt;
                  &lt;constraints nullable="false"/&gt;
              &lt;/column&gt;
          &lt;/createTable&gt;
          &lt;createTable tableName="new_table"&gt;
              &lt;column name="id" type="int"&gt;
                  &lt;constraints primaryKey="true" nullable="false"/&gt;
              &lt;/column&gt;
          &lt;/createTable&gt;
      &lt;/changeSet&gt;
  
  &lt;/databaseChangeLog&gt;
  </code></pre>
  
  <p>I've created a clean schema and i've launched the migrate command.</p>
  
  <p>Liquibase created the database, with the support tables databasechangelog and ..lock.</p>
  
  <p>Now how i can track the changes?? i've modified the changeset adding a new createTable element but when i try the command "update" liquibase tells me this</p>
  
  <pre><code>Migration Failed: Validation Failed:
       1 change sets check sum
  </code></pre>
  
  <p>so i don't think to have understood the way to work with liquibase.</p>
  
  <p>Someone may point me to the right direction??</p>
  
  <p>Thanks</p>