SELECT * FROM [dbo].[Product]
WHERE [CategoryID] IN (
SELECT [CategoryID] FROM [dbo].[Category] WHERE [CategoryID] <= 10
)这段没有看懂,感觉和 SELECT * FROM [dbo].[Product]
WHERE [CategoryID] WHERE [CategoryID] <= 10是一样的
WHERE [CategoryID] IN (
SELECT [CategoryID] FROM [dbo].[Category] WHERE [CategoryID] <= 10
)这段没有看懂,感觉和 SELECT * FROM [dbo].[Product]
WHERE [CategoryID] WHERE [CategoryID] <= 10是一样的
但是如果Product.CategoryID的值是1、2、3、4、5,Category.CategoryID的值只有1、2、3,那就不一样了。