使用 CodeIgniter 的 ActiveRecord 计算具有特定列值的行数

Question

如何使用 CodeIgniter 的查询生成器方法编写以下 SQL？

SELECT COUNT(*) AS total
FROM comments
WHERE `level`= 4

Answer 1

$this->db->select('count(*)');
$this->db->from('comments');
$this->db->where('level','4');
$query = $this->db->get();
echo $query->num_rows();

Answer 2

    $this->db->select('count(*) as total');  
    $this->db->from('comments');
    $this->db->where('level', 4);
    $sql   = $this->db->return_query();
    /*debug*/ 
    /*echo 'sql:: '.$sql;*/
    $query = $this->db->get(); 
    $arr   = $query->row_array(); 
    $total = $arr['total'];  

Answer 3

$query = $this->db->query("SELECT COUNT(*) AS total FROM comments WHERE `level`= 4");
echo $query->result_array();

或

$this->db->query("SELECT COUNT(*) AS total FROM comments");
$this->db->where("`level`= 4");

Answer 4

您可以随时使用

$this->db->query('SELECT COUNT( * ) AS total FROM comments WHERE `level`= 4');

Answer 5

我想你会喜欢这样的：

$count = $this->db->where("level","4")->count_all_results("comments");

http://codeigniter.com/user_guide/database/active_record.html