在w3schools这题 https://bit.ly/2D7WLmn 范例中
SELECT SupplierName
FROM Suppliers
WHERE EXISTS (SELECT ProductName FROM Products
WHERE Products.SupplierID = Suppliers.supplierID AND Price < 20);
会得到 24 个 SupplierName的结果
但是如果我改写成
SELECT SupplierName
FROM Suppliers
WHERE EXISTS (SELECT ProductName FROM Products,suppliers
WHERE Products.SupplierID = Suppliers.supplierID AND Price < 20);
会得到 29 个 SupplierName的结果
多出来的五笔资料Price都 > 20
不知道两个SQL语法的差别在哪里，恳请大大指导