title: Select all result from first table without matching with second table
body: <p>I have 2 tables one is  user table and another is rating table which have the mapping data of user rating</p>
  
  <p><strong>user table</strong></p>
  
  <pre><code>user_id |  firstname | lastname
  --------------------------------
  1       | 1test      | 1test lname
  2       | 2test      | 2test lname
  3       | 3test      | 3test lname
  4       | 4test      | 4test lname
  5       | 5test      | 5test lname
  </code></pre>
  
  <p><strong>rating table</strong></p>
  
  <pre><code>user_id |  rating
  ------------------
  1       |   4
  2       |   3
  3       |   5
  1       |   4
  </code></pre>
  
  <p>In result i need avg value of rating with user info in one query</p>
  
  <pre><code>user_id |  firstname | lastname      | rating
  ---------------------------------------------
  1       | 1test      | 1test lname   |  4
  2       | 2test      | 2test lname   |  3
  3       | 3test      | 3test lname   |  5
  4       | 4test      | 4test lname   |  0
  5       | 5test      | 5test lname   |  0
  </code></pre>