title: How can I make sure no duplicate row is inserted
body: <p>I have a table in Oracle:</p>
  
  <pre><code>NAME     DATE      TIMEOFDAY    PAYMENT
  SUBIR   10-08-12      DAY        10000 
  SUBIR   10-08-12      NIGHT      12000
  </code></pre>
  
  <p>Now I want to make modification in the oracle table so that a single user cannot <code>pay</code> more than once in a particular day. For example, I cannot insert like:</p>
  
  <pre><code>NAME     DATE      TIMEOFDAY    PAYMENT
  SUBIR   10-08-12      DAY        10000 
  SUBIR   10-08-12      NIGHT      12000
  SUBIR   10-08-12      DAY        14000
  </code></pre>
  
  <p>The 3rd row should not be inserted after the previous two records as there is already a payment that has been made in <code>day</code> on <code>10-08-12</code>. So how can I make this function in the oracle table?</p>
  
  <p><strong>EDIT</strong>- I guess I have to make <code>date</code> and <code>timeofday</code> compositely <code>unique</code>. Is it possible? The reason behind my such thinking is if I make both of them <code>unique</code> separately, users will not be allowed to enter a row with the same date for the second time but with different <code>timeofday</code>. </p>