Learning objectives:1. Understanding the thinking of database designIi. Know what e-r3. E-r maps capable of being tailored to operational needsLearning process:Today we briefly present theoretical knowledge of database modelling, while providing some simple examples of how our database tables were designed. Today's main learning goals are:This lesson begins with an important step in database designthe design of e-r maps。I. Why a data mount

It is estimated that an umbrella existed over 3,000 years ago. But since then, the design of the umbrella has remained largely unchanged and is made up of skeletons and fabrics. The new air umbrella (air umbrella), which appeared on the crowd-sourced website kickstarter, has broken the original design and used air from the umbrella centre to prevent the rain。But it's not the first time that this idea has been put forward, and in 2010 one o