title: sql Query Where optimization
body: <p>I have written 2 quarries, which are </p>
  
  <p>1) <code>Select c,c2,c3,c4,c5,c6... from table1 where Id is NULL;</code></p>
  
  <p>In table1 there are 10000's of records and column Id doesn't have null value. This query takes 5 min. to execute. And </p>
  
  <p>2) <code>Select c,c2,c3,c4,c5,c6... from table1 where Id = 'abvccdhu9887687698';</code></p>
  
  <p>this query takes less than a second.</p>
  
  <p>How this time difference is occurs </p>
  
  <p>Please help me..I am waiting for your valuable suggestions </p>