title: Liquibase Add Unique Constraint During Table Creation
body: <p>I want to add a unique constraint to my table during it's creation.
  I thought something like this would work but it seems to just do nothing.</p>
  
  <pre><code>&lt;createTable tableName="MY_TABLE"&gt;
     &lt;column name="MY_TABLE_ID" type="SMALLINT" autoIncrement="true"&gt;
        &lt;constraints primaryKey="true" nullable="false"/&gt;
     &lt;/column&gt;
     &lt;column name="TABLE_FIELD" type="SMALLINT"&gt;
        &lt;constraints nullable="false" uniqueConstraintName="TABLE_FIELD_ix1"/&gt;
     &lt;/column&gt;
     &lt;column name="TABLE_FIELD_TWO" type="SMALLINT"&gt;
        &lt;constraints nullable="false" uniqueConstraintName="TABLE_FIELD_ix1"/&gt;
     &lt;/column&gt;
  &lt;/createTable&gt;
  </code></pre>
  
  <p>I know I can use the addUniqueConstraint tag (and have successfully used it) after I create the table but I wanted to know if that was avoidable.</p>
  
  <p>Basically I want to do this but during the create table portion</p>
  
  <pre><code>&lt;addUniqueConstraint tableName="MY_TABLE"
                       columnNames="TABLE_FIELD, TABLE_FIELD_TWO"
                       constraintName="TABLE_FIELD_ix1"/&gt;
  </code></pre>