需要帮助来构建一个codeigniter数据库查询

Question

我想使用codeigniter query_builder函数。没有想法，请帮助。

$this->db->query("SELECT city as popularcity FROM(SELECT city,count(city) as
countcity FROM ads LIMIT 0, 6) as t ORDER BY MAX(countcity)");

Answer 1

$this->db->query("SELECT city as popularcity, countcity 
FROM 
(SELECT city, count(city) as countcity FROM ads GROUP BY city) as t
ORDER BY countcity DESC LIMIT 0, 6");

Answer 2

尝试以下代码，

$this->db->select("city as popularcity, countcity"); 
$this->db->from("(SELECT city, count(city) as countcity FROM ads GROUP BY city) as t");
$this->db->order_by("countcity DESC");
$this->db->limit(0,6);