Fetch data from multiple tables
I am getting the output but I am not sure if this is correct. I saw one or two solution using joins So I am confused that whether the query I have written is correct or not


It is a good practice to use JOIN : Explicit vs implicit SQL joins.

Second you could use aliases so you do not have to type entire table name.

SELECT  SUM(po.quantity)         AS TotalQuantity
       ,SUM(po.quantity*p.price) AS TotalSaleAmount 
FROM productorder po
JOIN product p
  ON po.ProductId = p.ProductId 
JOIN `order` o
  ON o.OrderId = po.OrderId 
WHERE o.OrderDate = CURDATE();


SqlFiddleDemo