这个codeigniter查询如何执行？

Question

Is this (1):

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

same as this (2)

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

The codeigniter method chained query I used to produce the result (1) is

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

and to produce (2) I used this

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

Could someone please explain the best way(from the above) to write CI query? Does AND get first priority here in the first example?

Answer 1

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

this code make query like

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

so it yields wrong result as per your expectation result. fourth one is correct. you can use it.

Answer 2

This is the best way

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

Just remember 1 thing that in short AND is multiplication, OR is addition so as per bodmas rule AND is on priority. This is some sort of practical example which we follow in our coding. So always separate AND, OR glue with brackets like:

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