title: what is selecttype and type when used EXPLAIN in mysql and how i can increase the performance using these results
body: <p>I saw in some places we can see the query details in mysql by using EXPLAIN keyword.
       I am able to see the details.But what <code>selecttype</code> and <code>type</code> and <code>possiblekeys</code> says exactly? and how i can increase performance of my query with the details provided by <code>EXPALIN</code>.</p>
  
  <p>Thanks in advance....</p>