Relational Schema. CS 4700/6700 A Sample of Small Database Design Using Microsoft Access

Transcription

1 CS 4700/6700 A Sample of Small Database Design Using Microsoft Access Company relational database schema from the textbook (Fundamentals of Database systems, 6 th Edition, by Ramez Elmasri and Shamkant Navathe) is used to illustrate as an example throughout this tutorial. The relational schema shows below in accordance with the Figure 3.7 in the textbook. Relational Schema EMPLOYEE Fname Minit Lname Ssn Bdate Address Sex Salary Super_ssn Dno DEPARTMENT Dname Dnumber Mgr_ssn Mgr_start_date DEPT_LOCATIONS Dnumber Dlocation PROJECT Pname Pnumber Plocation Dnum WORKS_ON Essn Pno Hours DEPENDENT Essn Depentdent_name Sex Bdate Relationship

2 1. Creating a New Database When you open Microsoft Access 2013 it should look like Figure 1. To create a new database, you can choose Blank desktop database. Figure 1 Type the name of the database in File Name box of the pop-up window. To save the database at a different location, click on the highlighted folder symbol. Once the database name is entered click on the Create button. Here the database is named Company as shown in Figure 2.

3 Figure 2 Once the Create button is clicked Access will be as shown in Figure 3. Figure 3

4 2. Creating New Tables Click Create first, then in the sub tab, click on Table. Figure 4 shows how it should appear when you do the above. Actually, Table 1 is created by default before you creating a new table. Figure 4 Now under the tab Home or tab Fields, click on View and select Design View. Then in the pop-up window as shown in Figure 5, type the table name and click OK. Here, EMPLOYEE is entered as the table name.

5 Figure 5

6 Once you click OK in previous step, you can start entering the field names or attribute names and specify the data type from the drop down menu as shown in Figure 6. By default it sets the first attribute you entered as the primary key. To mark or unmark any of the fields as a primary key, click on the highlighted primary key symbol. Figure 6 Note: To mark two or more attributes as primary keys, first unmark the already existing primary key by selecting the attribute marked as the primary key and click on the Primary Key symbol highlighted in Figure 7 (optional). Then select the two or more attributes you want to set as primary keys, for instance, Dnumber and Dlocation shown in Figure 7. At last, click on the Primary Key symbol.

7 Figure 7 In the encircled area shown in Figure 8, constrains can be made on the input data of attributes. For example, in Figure 8, the Field Size of Sex is set to be 1. And The Validation Rule is set to be M or F or U which means that the input of attribute Sex can only be M, F or U for unknown. When the input data are invalid, the message in Validation Text will be popped up to remind users.

8 Figure 8 After inputting all the field names of a table and their data types, click on View and select Datasheet View.

9 Figure 9 Once you select the Datasheet View, the dialogue box shown in Figure 10 pops up, asking if you want to save the table. Select Yes.

10 Figure 10 Once Yes is selected, a datasheet appears as in Figure 11. Here you can start entering data row by row in the EMPLOYEE table. Figure 11

11 Repeat all the steps of Creating New Tables, you can create all other tables in your database. And the completed database looks like Figure 12. Input data comes from the Figure 3.6 in the textbook. Figure 12

12 3. Adding Relationships Once all the tables of the database are created, we need to specify referential integrity constraints. To do this, click on Database Tools and select Relationships. Figure 13 When Relationships is clicked, the Show Table window pops up as in Figure 14. Or you can open the Show Table by clicking on the highlighted symbol.

13 Figure 14 In the Show Table, select all tables you want to establish relationships then click the Add button. These tables will appear on the background board as shown in Figure 15. Once you have finished adding tables, click on the Close button to close the Show Table.

14 Figure 15 The referential integrity constraint between two relations can be specified by dragging the primary key attribute of one table (e.g., Ssn in the EMPLOYEE table) to the foreign key attribute of the other table (e.g., Essn in the WORKS_ON table). Then Edit Relationships window appears like Figure 16. Make sure that the relationship is made between appropriate attributes by checking the attribute and table names in the Table/Query and Related Table /Query. Sometime by dragging operations, unrelated attributes may be connected incorrectly, so always check the attribute names before clicking on Create. Once you click on Create, a line connecting these two attributes will appear as shown in Figure 17.

15 Figure 16 Figure 17

16 Repeat the same procedures in adding relationships to other tables in the database. Figure 18 presents the final result when all the relationships have been established. Note that if a relationship is needed between attributes in the same table, a copy of the table should be generated like table EMPLOYEE_1 in Figure 18. Moreover when there is more than one relationship between two tables, like EMPLOYEE and DEPARTMENT, then a copy of one of the table is also need to be created. And the copy table is still EMPLOYEE_1 in this more than one relationship situation. Figure 18 To exit from Relationship Tools, click on any of the encircled areas in Figure 19. A dialogue box asking Do you want to save changes to the layout of relationships appears. Click on Yes.

17 Figure Writing Queries To start writing queries, click on Create then Query Design. Figure 20

18 Click on Close to close the pop-up Show Table window. Figure 21 Now click on SQL View then select SQL SQL View. Figure 22

19 Once SQL SQL View is selected, Figure 23 appears. SQL queries can be written on the provided space as shown below. To run the query, click the! run button. Figure 23 Some sample queries is used as illustrations. Query 1: Retrieve the name and address of all employees who work for the Research Department.

20 Figure 24 After running the query, the result will show on the screen as in Figure 25. Figure 25

21 Query 2: Retrieve the name of each employee who works on all the projects controlled by department 4. Figure 26 Result of this query is shown in Figure 27. Figure 27

22 Query 3: For each project, retrieve the project number, the project name and the number of employees who work on that project. Result of this query is shown as: Figure 28 Figure 29