计算codeigniter选择查询中特定列的平均值

Question

I want to calculate average of a specific column, for eg. rating column for that i am writing the following query but it is giving me syntax error in the query, Please help to solve my problem.

$this->db->select('*, AVG(`rating`) As avg_r');

Answer 1

尝试这个：

$this->db->select('id, name, email, AVG(rating) as avg_r');

Answer 2

CodeIgniter by default protect field you can disable the protection by passing one extra second parameter.

$this->db->select('*, AVG(`rating`) As avg_r',FALSE);

as $this->db->select() accepts an optional second parameter. If you set it to FALSE, CodeIgniter will not try to protect your field or table names with backticks

For More info you can refer Active record documentation https://ellislab.com/codeigniter/user-guide/database/active_record.html