在 CodeIgniter 查询生成器中使用子查询编写查询？

Question

我的以下查询与查询生成器有问题。

SELECT Sum(TEMP.total) AS total_amount
FROM   (SELECT Ifnull(t3.amount, t1.amount) AS total
        FROM   table1 AS t1
               LEFT JOIN table2 AS t2
                      ON t2.class = t1.class
               LEFT JOIN table3 AS t3
                      ON t3.student = t2.student
                         AND t3.type = t1.type) AS TEMP

有什么方法可以使用查询生成器来实现吗？我目前正在使用方法。

Answer 1

请检查一下，希望对您有所帮助

$this->db->select('IFNULL(t3.amount, t1.amount) as total');
$this->db->from('table1 as t1');
$this->db->join('table2 as t2', 't2.class = t1.class', 'LEFT');
$this->db->join('table3 as t3', 't3.student = t2.student AND t3.type = t1.type', 'LEFT');
// $this->db->get();
$lastquery = $this->db->last_query();

$this->db->select('SUM(TEMP.total) as total_amount');
$this->db->from('('.$lastquery.') as TEMP');
$result = $this->db->get()->result_array();

Answer 2

如果您的mysql查询没问题，请使用此方法进行运行这样复杂的查询。

$sql = "Your Query";
$qr = $this->db->query($sql);
return $qr->row();

如果仍然没有得到输出，请先检查 from 子句中的子查询。

Answer 3

不要使用 get() 后跟 last_query() 因为 get() 实际上运行数据库查询。

相反，使用 get_compiled_select() 将 returns 无需运行查询的查询。

$this->db->select('IFNULL(t3.amount, t1.amount) as total');
$this->db->from('table1 as t1');
$this->db->join('table2 as t2', 't2.class = t1.class', 'LEFT');
$this->db->join('table3 as t3', 't3.student = t2.student AND t3.type = t1.type', 'LEFT');
$subquery = $this->db->get_compiled_select();


$this->db->select('SUM(TEMP.total) as total_amount');
$this->db->from('('.$subquery.') as TEMP');
$result = $this->db->get()->result_array();

默认情况下 get_compiled_select() 将重置查询生成器。

See the docs.

在 CodeIgniter 查询生成器中使用子查询编写查询？

Write query with subquery in CodeIgniter Query Builder?

php

codeigniter

query-builder