如何计算年龄等于一定数量的人数？ [关闭]

Question

How to count number of people, whose age equals, for example, 18 years old?

<?php $emp_query=mysql_query("SELECT
  'employeeID',
  `LastName`,
  `birthday`,
  (YEAR(CURRENT_DATE)-YEAR(`birthday`))-(RIGHT(CURRENT_DATE,5)<RIGHT(`birthday`,5)
  ) AS `age`
FROM `employee`
ORDER BY `LastName`");
while($row=mysql_fetch_array($emp_query)){ $id=$row['employeeID']; ?>
                <td><?php echo $row['LastName']; ?></td>
                            <td><?php echo $row['birthday']; ?></td>
                            <td><?php  echo $row['age']?></td>

<?php } ?>

Answer 1

If you are satisfied with your age calculation, then you can rephrase the query as:

SELECT COUNT(*)
FROM (SELECT (YEAR(CURRENT_DATE)-YEAR(`birthday`))-(RIGHT(CURRENT_DATE,5)<RIGHT(`birthday`,5)
             ) AS `age`
      FROM `employee`
     ) e
WHERE age = 18;