how to join the tables in mysql databases; code example

Example 1: mysql join two tables

SELECT user_id, user_name
FROM users
UNION
SELECT organization_id, organization_name
FROM organizations

Example 2: how to join result table in mysql

SELECT inv.product_id, inv_stock.stock
FROM inventories AS inv

JOIN 

(SELECT product_id, stock
FROM inventories ) AS inv_stock

ON inv.product_id = inv_stock.product_id
 ;