kc弟8讲数据库规范化理论.ppt

第8讲: (第7章) 关系数据库设计：规范化理论(一) 重庆大学计算机学院 课程名称: 数据库系统 -------------------- Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 第8讲：关系数据库设计：规范化理论(一) 项目驱动目标： 如何得到一个优化的关系数据库结构！ 一、良好关系模式的标准 ? 二、第一范式(1NF) ? 三、函数依赖 ? 四、巴赫范式第三范式 ? 五、规范化基础理论 ? 主要讨论问题： 好的关系模式有什么标准 什么是第一范式(1NF) 什么是函数依赖，有何作用 什么是BCNF 和第三范式 什么是函数依赖集的闭包，有何作用 什么是属性集的闭包，有何作用 Exercise 8 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. The Banking Schema - 根据ER图获得的 branch = (branch_name, branch_city, assets) customer = (customer_id, customer_name, customer_street, customer_city) loan = (loan_number, amount) account = (account_number, balance) employee = (employee_id. employee_name, telephone_number, start_date) dependent_name = (employee_id, dname) - - - account_branch = (account_number, branch_name) loan_branch = (loan_number, branch_name) borrower = (customer_id, loan_number) depositor = (customer_id, account_number, access_date) cust_banker = (customer_id, employee_id, type) works_for = (worker_employee_id, manager_employee_id) - - - payment = (loan_number, payment_number, payment_date, payment_amount) - - - savings_account = (account_number, interest_rate) checking_account = (account_number, overdraft_amount) 一 良好关系模式的标准 1-1 这是最终的数据结构？ 1-2 好的结构有无判定标准？ 问题1答案 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 随意地 Combine Schemas Suppose we combine borrower and loan to get bor_loan = (customer_id, loan_number, amount ) Result is possible repetition of information (L-100 in example below) 1-3 模式可以合并吗？ 良好关系模式的标准 可能会产生数据冗余！ 返 回 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. A Combined Schema Without Repetition Consider combining loan_branch and loan loan_amt_br = (loan_number, amount, branch_name) No repetition重复 (as sugges