Mysql选择多列到单列

Question

I need to change the three columns in to single column with all of the data can any one help

This is my Query

SELECT emp_id
     , testing_emp_id
     , bug_emp_id 
  FROM tbl_screen_incharge 
 WHERE project_id = "PRJ0016" 
   AND (emp_id!="" OR testing_emp_id!="" OR bug_emp_id!="" )
 GROUP 
    BY emp_id 
     , testing_emp_id
     , bug_emp_id;

Answer 1

you can use UNION for this:

SELECT `tbl_screen_incharge`.`emp_id`
FROM `tbl_screen_incharge`
UNION
SELECT `tbl_screen_incharge`.`testing_emp_id`
FROM `tbl_screen_incharge`

I have tested this using my database.