title: How to make a pair of columns unique in mysql
body: <pre><code>+----+---------------+-------+---------------+
  | id |     name      | phone |    ip_addr    |
  +----+---------------+-------+---------------+
  |  1 | customname001 |  1234 | 192.168.100.1 |
  |  2 | customname002 |  2156 | 192.168.100.2 |
  |  3 | customname003 |  9685 | 192.168.100.3 |
  |  4 | customname004 |  1546 | 192.168.100.1 |
  |  5 | customname005 |  1234 | 192.168.100.1 |
  +----+---------------+-------+---------------+
  </code></pre>
  
  <p>In my codeigniter project I am trying to build a model which will help me insert a new row into a table which looks something like the above one. The condition I want to apply here is to check if the combination of name, phone and ip_addr is unique or not.</p>
  
  <p>I know that for a single column if we set the value to be unique then the values can't be repeated but my example is a different case where I want the combination of all the columns(except the id) to be unique.</p>
  
  <p>Can anyone help me here in building the model which will help me to add new pair of name, phone and ip_addr and check if the pair already exists and accordingly give a feedback.</p>