SQL语句查询技术，我们在开始创建数据表和向表中插入演示数据之前，我想给大家解释一下实时数据表的设计理念，这样也许能帮助大家能更好的理解SQL查询，在数据库设计中，有一条非常重要的规则就是要正确建立主键和外键的关系。-Before we begin creating tables and insert data into the table presentation, I would like to explain to you the concept of real-time data table design, so that may help us to better understand SQL queries in the　design, it has a very important the rule is to establish the correct relationship between the primary keys and foreign keys.