Question

这是（1）：

SELECT `message`, `from` FROM (`chat_messages`) WHERE `from` = '1' AND `delivered` = 1 OR `to` = '1' AND `delivered` = 1

与此（2）相同

SELECT `message`, `from` FROM (`chat_messages`) WHERE (`from` = '1' AND `delivered` = 1) OR (`to` = '1' AND `delivered` = 1)

用于生成结果（1）的codeigniter方法链式查询是

$this->db->select('message,from')->from('chat_messages')->where(array('from' => $user, 'delivered' => 1))->or_where('to', $user)->where('delivered', 1);

并且生产（2）我使用了这个

$where = "(`from` = '1' AND `delivered` = 1) OR (`to` = '1' AND `delivered` = 1)";
$this->db->select('message,from')->from('chat_messages')->where($where);

有人可以解释一下编写CI查询的最佳方法（从上面开始）吗？ AND在第一个例子中是否优先考虑？

Answer 1

$this->db->select('message,from')->from('chat_messages')->where(array('from' => $user, 'delivered' => 1))->or_where('to', $user)->where('delivered', 1);

此代码使查询类似

from = 'somthing' and delivered='something' or to='something' and delivered='something'

因此根据您的预期结果会产生错误的结果。第四个是正确的。你可以使用它。

Answer 2

这是最好的方法

$where = "(`from` = '1' AND `delivered` = 1) OR (`to` = '1' AND `delivered` = 1)";
$this->db->select('message,from')->from('chat_messages')->where($where);

请记住1件事，简而言之就是乘法，或者是加法，因此根据bodmas规则并优先考虑。这是我们在编码中遵循的某种实际例子。所以总是将AND，OR粘合在一起，如下所示：

(`from` = '1' AND `delivered` = 1) OR (`to` = '1' AND `delivered` = 1)

这个codeigniter查询如何执行？

2 个答案: