MYSQL query for selecting the result of a condition of one table and showing it on another table [closed]

Answer 1

-- INSERT INTO item_details
--  or
-- CREATE TABLE item_details
SELECT   stock_name, SUM(CASE type
           WHEN 'PURCHASE' THEN +quantity
           WHEN 'ISSUE'    THEN -quantity
         END) AS quantity
FROM     stock_details
GROUP BY stock_name