issues in table alias in codeigniter - mysql

Question

Here, I am creating an alias for the inner selection, but it automatically adds the table prefix to the alias table. My sql query is as follows:
SELECT
`tb1`.*, `tb2`.*, `tb3`.`client_name`,
`cms_tb4`.*, `tb1`.`project_status` AS pstat
FROM
(`cms_projects` tb1)
JOIN `cms_project_type` tb2 ON `tb2`.`id` = `tb1`.`project_type`
JOIN `cms_clients` tb3 ON `tb1`.`client_id` = `tb3`.`client_id`
JOIN (
SELECT
*
FROM
(
SELECT
t1.project_id AS projid,
t2.work_id,
t2.work_date
FROM
cms_projects_mod t1,
cms_work_status_emp t2
WHERE
t1.module_id = t2.pro_module_id
ORDER BY
t2.work_date DESC
) AS subtb4
GROUP BY
projid
ORDER BY
work_date DESC
) AS tb4 ON `cms_tb4`.`projid` = `tb1`.`project_id`
LIMIT 50
i am working on codeigniter framework.
in codeigniter model just like this
$this->db->select('tb1.*');
$this->db->select('tb1.project_status as pstat');
$this->db->from('cms_projects tb1');
$this->db->join('project_type tb2', 'tb2.id=tb1.project_type');
$this->db->join('clients tb3', 'tb1.client_id = tb3.client_id');
$this->db->join("(
select * from (
select t1.project_id as projid, t2.work_id,t2.work_date from cms_projects_mod t1, cms_work_status_emp t2 where t1.module_id = t2.pro_module_id order by t2.work_date desc) as subtb4
group by projid order by work_date desc ) as tb4 ",
"tb4.projid = tb1.project_id" ,false);
$this->db->group_by("tb1.project_id");
$this->db->order_by("tb3.work_date",'desc');
here i didn't give any prefix in third join tb4 but CI Add automatically when the running time.

Answer 1

Please check the code order in CodeIgniter Documentation.
$this->db
->select()
->from()
->join()
This is the correct order. Changing the order sometimes causes issues in complex queries.
Visit this link https://github.com/bcit-ci/CodeIgniter/issues/2975

Answer 2

Why you using query strings? If you using coeignoter why dont you use active record. Active Record queries are automatically protected with sql injection.
you can do kind of this....its not same you want just idea how you can use active record sql.
$query = $this->db->select('*',FALSE)
->from('tb1','tb2'.....)
->join('tb2', 'tb1.cms_project_type = tb2.cms_project_type','left')
->join('tb3', 'tb1.cms_project_type = tb2.cms_project_type','left')
->group_by('projid')
->order_by('work_date','DESC')
->get();
https://ellislab.com/codeigniter/user-guide/database/queries.html
Hope this help.