title: How to drop check constraint in sql
body: <p>All I need to know is how to drop check and primary key constraint on my table.</p>
  
  <p>Here is my table schema.</p>
  
  <pre><code>create table time_slot
    (time_slot_id    varchar(4),
     day      varchar(1),
     start_hr    numeric(2) check  (start_hr &gt;= 0 and start_hr &lt; 24),
     start_min    numeric(2) check (start_min &gt;= 0 and start_min &lt; 60),
     end_hr      numeric(2) check (end_hr &gt;= 0 and end_hr &lt; 24),
     end_min    numeric(2) check (end_min &gt;= 0 and end_min &lt; 60),
     primary key (time_slot_id, day, start_hr, start_min)
    );
  </code></pre>