title: COUNT() and EXPLAIN row's count are getting different
body: <p>In Mysql, I have a table (employee_by_range). I am getting rows using <code>count</code> and <code>explain</code></p>
  
  <p><em>when am i trying to get rows using <code>COUNT()</code>, it's return <strong>15880256</strong> rows</em></p>
  
  <pre><code>mysql&gt; select count(1) from test.employee_by_range;
  +----------+
  | count(1) |
  +----------+
  | 15880256 |
  +----------+
  1 row in set (4.80 sec)
  </code></pre>
  
  <p><em>when am i trying to get rows using <code>EXPLAIN</code> it's return <strong>27912636</strong> rows</em> </p>
  
  <pre><code>mysql&gt; explain select emp_id from test.employee_by_range;
  +----+-------------+-------------------+------+---------------+------+---------+------+----------+-------+
  | id | select_type | table             | type | possible_keys | key  | key_len | ref  | rows     | Extra |
  +----+-------------+-------------------+------+---------------+------+---------+------+----------+-------+
  |  1 | SIMPLE      | employee_by_range | ALL  | NULL          | NULL | NULL    | NULL | 27912636 | NULL  |
  +----+-------------+-------------------+------+---------------+------+---------+------+----------+-------+
  1 row in set (0.00 sec)
  </code></pre>
  
  <p>Why both row's count are different ? </p>