本书讲述了关系数据库之间通信的标准计算机语言SQL语言，如果希望掌握关系数据库理论和实践知识，本书会带给你意想不到的收获。-This book describes the communication between the relational database standard computer language SQL language, if you want to master the knowledge of relational database theory and practice, this book will bring you unexpected results.