title: Finding records which doesn't exists in other oracle table
body: <p>I am trying to find records which exists in table A but not in table B. If there is only one column to check, then I can use </p>
  
  <pre><code>select col_A,col_B,......from A where col_A not in (select Col_A from B).
  </code></pre>
  
  <p>But I have four columns which need to checked.</p>
  
  <p>I did something like this, which works but is not the perfect way</p>
  
  <pre><code>select col_A,col_B,col_C,col_D from A where col_A||col_B||col_C||col_D not in (select col_A||col_B||col_C||col_D from B)
  </code></pre>
  
  <p>and also it takes lot of time to return results in case of large amount of data.</p>
  
  <p>Please suggest the proper way of doing this.</p>
  
  <p>Thanks.....</p>