MySQL将两列合并为一列，另一行

Question

I have following output

+--------------+---------------+-----------+-----+--------------+
| officer_name | supplier_name | item_name | qty | order_status |
+--------------+---------------+-----------+-----+--------------+
| A            | S1            | B5        |  21 | purchase     |
| B            | S1            | B5        |  20 | purchase     |
| C            | S2            | B5        |  -2 | issue        |
| D            | S3            | B5        |  -1 | issue        |
| A            | S2            | B5        |  -1 | issue        |
| A            | S2            | B5        |  -1 | issue        |
| B            | S4            | B5        |  -1 | issue        |
| C            | S4            | B5        |  -1 | issue        |
| D            | S3            | B5        |  -1 | issue        |
| A            | S3            | B5        |  -1 | issue        |
+--------------+---------------+-----------+-----+--------------+

This output has generated using following query

SELECT
store_officer.officer_name,
tbl_supplier.supplier_name,
store_item.item_name,
store_update_stock_details.qty,
store_update_stock.order_status
FROM
store_update_stock
Inner Join store_officer ON store_officer.officer_id = store_update_stock.supplier
Inner Join tbl_supplier ON tbl_supplier.supplier_id = store_update_stock.supplier
Inner Join store_update_stock_details ON store_update_stock.update_stock_id = store_update_stock_details.update_stock_id
Inner Join store_item ON store_item.item_id = store_update_stock_details.item
WHERE
store_item.item_id =  '3'

Then I need to get the following output by combining columns "officer_name" & "supplier_name" as follows :

+------------------------------+-----------+-----+--------------+
| supplier_name / officer_name | item_name | qty | order_status |
+------------------------------+-----------+-----+--------------+
| S1                           | B5        |  21 | purchase     |
| S1                           | B5        |  20 | purchase     |
| C                            | B5        |  -2 | issue        |
| D                            | B5        |  -1 | issue        |
| A                            | B5        |  -1 | issue        |
| A                            | B5        |  -1 | issue        |
| B                            | B5        |  -1 | issue        |
| C                            | B5        |  -1 | issue        |
| D                            | B5        |  -1 | issue        |
| A                            | B5        |  -1 | issue        |
+------------------------------+-----------+-----+--------------+

What are the changes can be done in my query to get the desired output ?. Can anyone help me ?

Answer 1

You can use conditional CASE..WHEN expressions to determine accordingly.

SELECT
  CASE store_update_stock.order_status
      WHEN 'purchase' THEN tbl_supplier.supplier_name 
      ELSE store_officer.officer_name
  END AS supplier_officer_name, 
  store_item.item_name,
  store_update_stock_details.qty,
  store_update_stock.order_status
FROM
  store_update_stock
Inner Join store_officer 
  ON store_officer.officer_id = store_update_stock.supplier
Inner Join tbl_supplier 
  ON tbl_supplier.supplier_id = store_update_stock.supplier
Inner Join store_update_stock_details 
  ON store_update_stock.update_stock_id = store_update_stock_details.update_stock_id
Inner Join store_item 
  ON store_item.item_id = store_update_stock_details.item
WHERE
  store_item.item_id =  '3'

Answer 2

SELECT IF(store_update_stock.order_status = 'issue', store_officer.officer_name, tbl_supplier.supplier_name) `supplier_name / officer_name`, ...