INSERT, UPDATE & DELETE (safely)

Reading is half the job; you also change data. The three write statements:

INSERT INTO products (name, stock) VALUES (?, ?);
UPDATE products SET stock = stock + ? WHERE name = ?;
DELETE FROM products WHERE stock = 0;

Always pass values as ? parameters, never by formatting strings. "... name = '" + name + "'" is the door to SQL injection: a name like x'; DROP TABLE products;-- would run as code. With ? the value is only ever data. After writing, call con.commit().

Write restock(con, name, amount) that adds amount to the stock of the product called name (parameterized UPDATE + commit), then returns that product's new stock. Press Run.