title: Altering a column: null to not null
body: <p>I have a table that has several nullable integer columns.  This is undesirable for several reasons, so I am looking to update all nulls to 0 and then set these columns to <code>NOT NULL</code>. Aside from changing nulls to <code>0</code>, data must be preserved.</p>
  
  <p>I am looking for the <em>specific SQL syntax</em> to alter a column (call it <code>ColumnA</code>) to "<code>not null</code>".  Assume the data has been updated to not contain nulls.</p>
  
  <p>Using <em>SQL server 2000</em>.</p>