codeigniter，使用Case When for Where查询

我有这个查询，我想让它在codeigniter查询形式工作，所以想知道它是否可能。

这是我想在Codeigniter中以Codeigniter自己的方式实现的查询。

    use zorkif_next;
SELECT 
    `osp_job_status_track`.`StatusID`,
    `osp_job_status_track`.`SubStatusID`,
    `osp_job_sub_status`.`CurrentStatus`
FROM
    (`osp_job_details`)
        LEFT JOIN
    `osp_job_status_track` ON `osp_job_status_track`.`JobID` = `osp_job_details`.`JobID`
        LEFT JOIN
    `osp_job_status` ON `osp_job_status`.`StatusID` = `osp_job_status_track`.`StatusID`
        LEFT JOIN
    `osp_job_sub_status` ON `osp_job_sub_status`.`SubStatusID` = `osp_job_status_track`.`SubStatusID`
        LEFT JOIN
    `hr_employee_details` ON `hr_employee_details`.`EmployeeID` = `osp_job_details`.`AssignToEmployeeID`
        LEFT JOIN
    `osp_job_type` ON `osp_job_type`.`JobTypeID` = `osp_job_details`.`JobtypeID`
WHERE
    -- `isDefault` = 1
       --    AND 
    CASE WHEN `osp_job_status`.`StatusID` = 2 
    THEN  `osp_job_sub_status`.`CurrentStatus` = 3
    ELSE `osp_job_status`.`StatusID` >= 2
    END ;

$this->db->where($where);

? ?