如何从一个表的前一行(股票详细信息)中减去(或添加)一行..并在另一个表(商品详细信息)中显示结果..?
1st table:stock_details ----------+----------+----------- stock_name | quantity | type ------------+----------+---------- laddu | 200 | PURCHASE Ghee | 50 | ISSUE 2nd table:item_details ----------+---------- stock_name | quantity ------------+---------
-- 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