大家有人会画E/R表吗?就是用矩形代表entity,用菱形代表relationship,用椭圆代表attributes的?
我们老师出了两道很短的小题可是我就是不会做啊...!!!
题目如下:
这是四个table,冒号后面的是它的attributes
countries: name, area, population, gdp ("gross domestic product")
cities: name, population, longitude, latitude
rivers: name, length
seas: name, max depths

老师让我们画两个E/R图
1.each river crosses one or several countries
2.each river ends in another river or in a sea

我不会啊!!~

谁能帮帮我?晚上就交了...555