ActiveRecord Mysql 选择列为 Null答案

【问题标题】：ActiveRecord Mysql Select column as NullActiveRecord Mysql 选择列为 Null
【发布时间】：2014-05-27 06:53:58
【问题描述】：

我有这个查询：

  $this->db->select ( 'u.user_id as id, u.username, u.first_name as firstName, u.last_name as lastName,' . null . 'as client' );
  $this->db->from ( 'users u' );

但在执行相同的操作时，它显示为空列。

还有

  $this->db->select ( 'u.user_id as id, u.username, u.first_name as firstName, u.last_name as lastName, null as client' );

在users表中取null作为列名，报错为column not found。

虽然直接对mysql执行时，查询给出了预期的输出

SELECT u.user_id as id, u.username, u.first_name as firstName, u.last_name as lastName, null as client FROM users u

【问题讨论】：

标签： php mysql codeigniter activerecord

【解决方案1】：

试试这个：

  $this->db->select ( 'u.user_id as id, u.username, u.first_name as firstName, u.last_name as lastName',false);
  $this->db->from ( 'users u' );

false 告诉不要逃避查询。

【讨论】：

【解决方案2】：

select()的第二个参数需要传入FALSE

$this->db->select ( 'u.user_id as id, u.username, u.first_name as firstName, u.last_name as lastName, NULL as client' ,FALSE );
 $this->db->from ( 'users u' );

【讨论】：