title: how to add check constraints for date columns
body: <p>I am getting this error</p>
  
  <blockquote>
    <p>ORA-02438: Column check constraint cannot reference other columns</p>
  </blockquote>
  
  <p>when I am performing this query</p>
  
  <pre><code>alter table Issue
  modify Issue_Date not null check (Issue_Date &lt;= sys_date);
  </code></pre>
  
  <p>as well as I have to add this condition also (<code>issue_date&lt;return_date</code>);</p>
  
  <p>and when I tried this </p>
  
  <pre><code>alter table Issue
  add constraint ck_Issue_Date not null check (Issue_Date &lt;= sys_date);
  </code></pre>
  
  <blockquote>
    <p>ERROR ORA-00904: : invalid identifier</p>
  </blockquote>