使用UNION的MySQL查询

Question

$sql = "SELECT `employee`.`employee_id`, `employee`.`employee_pre_code`, `employee`.`employee_code`, `employee`.`employee_name`, `employee`.`active`, `designation`.`designation_name`, `employeetype`.`employee_type_name`, `supervisor`.`supervisor_id`, `incharge`.`incharge_id`, `subsection`.`subsection_id`, `section`.`section_id`, `floor`.`floor_id`, `unit`.`unit_id`, `attendance_summery`.`present_days`,`attendance_summery`.`working_days` 
          FROM `employee` LEFT JOIN `designation` ON `employee`.`designation_id`=`designation`.`designation_id` 
          LEFT JOIN `employeetype` ON `employee`.`employee_type_id` = `employeetype`.`employee_type_id`
          LEFT JOIN `supervisor` ON `supervisor`.`supervisor_id` = `employee`.`supervisor_id` 
          LEFT JOIN `incharge` ON `incharge`.`incharge_id` = `supervisor`.`incharge_id` 
          LEFT JOIN `subsection` ON `subsection`.`subsection_id` = `incharge`.`subsection_id` 
          LEFT JOIN `section` ON `section`.`section_id` = `subsection`.`section_id` 
          LEFT JOIN `floor` ON `floor`.`floor_id` = `section`.`floor_id` 
          LEFT JOIN `unit` ON `unit`.`unit_id` = `floor`.`floor_id`    
          WHERE `employee`.`unit_id` = '1' AND `employee`.`active` = 1 
UNION
        SELECT `employee`.`employee_id`, `employee`.`employee_pre_code`, `employee`.`employee_code`, `employee`.`employee_name`, `employee`.`active`, `designation`.`designation_name`, `employeetype`.`employee_type_name`, `supervisor`.`supervisor_id`, `incharge`.`incharge_id`, `subsection`.`subsection_id`, `section`.`section_id`, `floor`.`floor_id`, `unit`.`unit_id`, `attendance_summery`.`present_days`,`attendance_summery`.`working_days` FROM `employee` 
          LEFT JOIN `attendance_summery` ON `attendance_summery`.`employee_id` = `employee`.`employee_id` 
          WHERE `attendance_summery`.`payment_period_id` = 36 
          ORDER BY `employee`.`employee_name` ASC";

$query = $this->db->query($sql);
return $query->result_array();

A Database Error Occurred

Error Number: 1054

Unknown column 'attendance_summery.present_days' in 'field list'

But the column 'attendance_summery.present_days' exists.

I failed to find the problem with the query.

Can any one help.

Answer 1

attendance_summery table is not selected in the first query of the union.

You will have to add ;

LEFT JOIN `attendance_summery` ON `attendance_summery`.`employee_id` = `employee`.`employee_id

to the first select of your sql. You need to test each field and add them.

Answer 2

don't you think, attendance_summery table should not be a part of FROM clause of first query while it is part of select list ? I cant see attendance_summery table in FROM CALUSE which is miss!!

Answer 3

My main issue was to use multiple conditions in JOINing the tables. At last added two conditions when joining attendance_summery table with AND keyword which joins the rows that only matches $paymentPeriodId variable. That fulfilled what I wanted. Again thanks for Jerome Anthony and Nitin Tripathi . My updated query is as:

$sql = "SELECT `employee`.`employee_id`, `employee`.`employee_pre_code`, `employee`.`employee_code`, `employee`.`employee_name`, `employee`.`active`, `designation`.`designation_name`, `employeetype`.`employee_type_name`, `supervisor`.`supervisor_id`, `incharge`.`incharge_id`, `subsection`.`subsection_id`, `section`.`section_id`, `floor`.`floor_id`, `unit`.`unit_id`, `attendance_summery`.`present_days`, `attendance_summery`.`working_days` "
      . "FROM `employee` "
      . "LEFT JOIN `designation` ON `employee`.`designation_id`=`designation`.`designation_id`"
      . "LEFT JOIN `employeetype` ON `employee`.`employee_type_id` = `employeetype`.`employee_type_id`"
      . "LEFT JOIN `supervisor` ON `supervisor`.`supervisor_id` = `employee`.`supervisor_id`"
      . "LEFT JOIN `incharge` ON `incharge`.`incharge_id` = `supervisor`.`incharge_id`"
      . "LEFT JOIN `subsection` ON `subsection`.`subsection_id` = `incharge`.`subsection_id`"
      . "LEFT JOIN `section` ON `section`.`section_id` = `subsection`.`section_id`"
      . "LEFT JOIN `floor` ON `floor`.`floor_id` = `section`.`floor_id`"
      . "LEFT JOIN `unit` ON `unit`.`unit_id` = `floor`.`floor_id`"
      . "LEFT JOIN `attendance_summery` ON (`attendance_summery`.`employee_id` = `employee`.`employee_id` AND `attendance_summery`.`payment_period_id` = $paymentPeriodId )"
      . "WHERE `employee`.`unit_id` = '1' AND `employee`.`active` = '1' "
      . "ORDER BY `employee`.`employee_name` ASC"; 

      $query = $this->db->query($sql);
      return $query->result_array();