title: Pull recrods which is not available in another table codeigniter
body: <p>I am looking for query result where I can see only Table 1 data which is not in Table 2; Here is my table definition and data;</p>
  
  <p>Table 1</p>
  
  <pre><code>id  name    father name age
  1      a    a father    60
  2      b    b father    70
  3      c    c father    60
  4      d    d father    50
  5      e    e father    20
  6      f    f father    32
  7      g    g father    40
  </code></pre>
  
  <p>Table 2</p>
  
  <pre><code>id  account_amount
  1   42
  3   90
  5   80
  7   49
  </code></pre>
  
  <p>Now I want all those records from Table 1 which is either not available in Table 2 or its correspondence account_amount in Table 2 is less than 50. Here would be the required outout</p>
  
  <pre><code>id  name    father name age
  1      a    a father    60
  2      b    b father    70
  4      d    d father    50
  6      f    f father    32
  7      g    g father    40
  </code></pre>
  
  <p>Thanks in advance for solution query in codeigniter</p>