php - 计算多个字段

Question

我有一张桌子叫reservations. 我想计算所有firstName字段guestFirstName。

我试过了：

$records = $dbh->query('SELECT count(firstName, guestFirstName) from reservations')->fetchColumn;

这给了我一个错误。如何计算所有firstName, guestFirstName记录？

Answer 1

尝试以下操作：

$query =  'SELECT count(firstName) + count(guestFirstName) as total ' . 
                 'FROM reservations';
$result = $dbh->query($query)->fetch();

echo $result['total']

SQL Fiddle 验证这一点：http ://www.sqlfiddle.com/#!2/42bad/2

SQL 的COUNT()函数不计算NULL值。

感谢@ChaotiCc 的帮助

Answer 2

您需要对count()每一列，更改如下

'SELECT count(firstName) as total_firstname, count(guestFirstName) as guest_firstname from reservations'