数据查询语句是SQL语句的重要组成部分，合理使用数据查询语句，可以极大的简化应用程序编制、快速的定位分析数据库系统的故障，查询语句是编程人员与数据库管理人员必不可少的工具，通过试验，加深学生对查询语句基本概念的理解与掌握,最终达到灵活应用的目的。-Data query SQL statement is an important part of the rational use of data query, you can greatly simplify application programming, database systems fast fault location analysis, query and database programmer is an indispensable tool for managers, through the test to familiarize students with basic concepts of query understanding and mastery, and ultimately achieving flexible application purposes.