第 4 掌 概念数据库设计

绘图软件

• 使用 draw.io 绘制 E-R 图
• draw.io 初始界面，可以不选择存储
• 绘制完成后，最好保存、下载图形到本地磁盘
• 图形的保存格式，选择默认的 XML 格式
• 本地的绘图文件，后续可以在 draw.io 中打开继续编辑
• 左侧的绘图面板，选择【+更多图形】，找到【实体关系】

公司案例

需求：

• The company is organized into DEPARTMENTs. Each department has a name, number and an employee who manages the department. We keep track of the start date of the department manager. A department may have several locations.
• Each department controls a number of PROJECTs. Each project has a unique name, unique number and is located at a single location.
• We store each EMPLOYEE’s social security number (SSN), address, salary, sex, and birthdate.
  • Each employee works for one department but may work on several projects.
  • We keep track of the number of hours per week that an employee currently works on each project.
  • We also keep track of the direct supervisor of each employee.
• Each employee may have a number of DEPENDENTs.
  • For each dependent, we keep track of their name, sex, birthdate, and relationship to the employee.

概念数据库设计

要求：

• 在 dbms-demo 仓库下，创建 04-conceptual-db-design 目录
• 对上面的公司案例，找出所以实体和属性，用 draw.io 绘制 E-R 图
• 将图形保存为 01-company-entity.drawio
• 在上面工作的基础上，找出所有联系集，并对实体和属性做适当的修改
• 将图形保存为 02-company-relationship.drawio
• 在上面工作的基础上，细化联系集，标记联系的基数和参与度
• 将图形保存为 03-company-relationship.drawio
• 在上面工作的基础上，细化联系集，标记联系的属性、弱实体型和标识联系型
• 将图形保存为 04-company-relationship.drawio
• 在上面工作的基础上，整合出完整的 E-R 图
• 将图形保存为 05-company-entity-relationship.drawio
• 将上面的图形文件，放到 04-conceptual-db-design 目录下
• 提交代码仓库，推送到 bitbucket 远程代码仓库