title: Constraint violation error
body: <p>I have created this table as part of my assignment,</p>
  
  <pre><code>create table course (
      cnum char(4) primary key,
      title varchar(20),
      credits number(1)
  );
  </code></pre>
  
  <p>The table has this check constraint cnum_ck</p>
  
  <pre><code>cnum like '[a-z][0-9][0-9][0-9]'
  </code></pre>
  
  <p>When I tried to insert the following row</p>
  
  <pre><code>insert into course values('m130', 'xyz', 3);
  </code></pre>
  
  <p>It threw <code>check constraint cnum_ck violation error</code>. I'm not sure where I went wrong. Please help</p>