SQL（JOIN效率高）
select *
from Products
where ProductId = (select top 1 ProductId from OrderLines order by Quantity Desc)
select *
from Products
where CategoryId in (select CategoryId from Categories where Name != 'Electronics')
select *
from Products p
where (select sum(Quantity) from OrderLines o where o.ProductId = p.ProductId) > 5
SELECT Name as ProductName
FROM Products p
JOIN OrderLines o on p.ProductId=o.ProductId
GROUP BY Name
HAVING SUM(o.Quantity)> 5
SELECT
p.Name as ProductName,
c.Name as CategoryName,
(SELECT AVG(p2.Price) FROM Products p2 WHERE p2.CategoryID = c.CategoryID) AS AvgPriceInCategory
FROM Products p
JOIN Categories c ON p.CategoryID=c.CategoryID