More Skills 12 Create Indexes and Establish a One-to-One Relationship. To complete this database, you will need the following file:

Transcription

1 CHAPTER 2 Access More Skills 12 Create Indexes and Establish a One-to-One Relationship An index stores the location of records based on the values in a field. An index improves performance when the field is searched or sorted. A one-to-one relationship is a relationship where each record in one table can have only one corresponding record in the other table. In both tables, the field that relates the two tables must contain a unique value. Cypress Sun Resorts needs to store the employee passwords in a separate table to improve database security. To complete this database, you will need the following file: a02_employee_logons You will save your files as: a02_employee_logons_your_name a02_employee_logons_snip_your_name 1. Start Access, and then open a02_employee_logons. Save the database in your Access Chapter 2 folder as a02_employee_logons_your_name If the Security Warning bar displays, enable the content. 2. In the Navigation Pane, right-click the Employees table, and then in the shortcut menu, click Design View. Microsoft Access Chapter 2 - Building a Relational Database and Creating Forms More Skills: SKILL 12 Page 1 of 6

2 3. Click in the Last Name field, and then under Field Properties, click the Indexed box. Compare your screen with Figure 1. The Last Name field does not have an index. By default, only a table s primary key and any foreign keys used to create relationships have indexes. Last Name Indexed property set to No Figure 1 4. Click the displayed Indexed arrow, and then click Yes (Duplicates OK) 5. Save the table, and then switch to Datasheet view. In the first record, change Mary to your first name and Bilger to your last name. Click in any other record, and then compare your screen with Figure 2. The Last Name index was updated after you finished updating the first record. This index will improve performance whenever the Last Name field is searched or sorted. Notice that the second and third records contain the same last name Shields. Because employees may have identical last names, the index allows duplicate values. Microsoft Access Chapter 2 - Building a Relational Database and Creating Forms More Skills: SKILL 12 Page 2 of 6

3 First record edited Duplicate last name values Figure 2 6. Switch to Design view, and then click in the User Name field. Click the Indexed box, and then click the displayed Indexed arrow. In the displayed menu, click Yes (No Duplicates). Each employee must have a unique user name. Thus, the index will not allow duplicate values. The table s primary key has its own index that does not allow duplicate values. 7. Click Save, and then Close the table. Open the Employee Logons table in Datasheet view. Compare your screen with Figure 3. Each employee s logon a user name and password used to obtain access to secure services displays in the datasheet. Employee logons Figure 3 Microsoft Access Chapter 2 - Building a Relational Database and Creating Forms More Skills: SKILL 12 Page 3 of 6

4 8. Switch to Design view, and then click in the Password field. Under Field Properties, click in the Input Mask field, and then click the displayed Build button. 9. In the displayed Input Mask Wizard, click Password, and then click Finish. 10. Click Save, and then switch to Datasheet view. Notice that the values in the Password field are now masked by the asterisk (*) character. 11. Close the table. Display the Database Tools tab, and then in the Show/Hide group, click Relationships. 12. In the displayed Show Table dialog box, double-click Employees, and then double-click Employee Logons. Close the Show Table dialog box. 13. In the Employees table displayed in the Relationships window, drag the User Name field to the User Name field in the Employee Logons table. When the pointer displays, release the mouse button. 14. In the displayed Edit Relationships dialog box, click the Enforce Referential Integrity check box, and then click Create. Compare your screen with Figure 4. A one-to-one relationship is created. One-to-one relationship Figure Click Save, and then Close the Relationships window. Open the Employees table in Datasheet view. 16. To the left of the first record, click the Expand button, and then compare your screen with Figure 5. The related logon for the record with your name displays in a subdatasheet. A subdatasheet is a datasheet that displays the corresponding records from a related table. Here, the logon for the first record displays. Because the User Name field is common to both tables, the field displays in the datasheet, and it does not display in the subdatasheet. Microsoft Access Chapter 2 - Building a Relational Database and Creating Forms More Skills: SKILL 12 Page 4 of 6

5 Subdatasheet for Your Name Figure In the displayed subdatasheet for the first record, click in the displayed append row, and then type second 18. Press F, and then compare your screen with Figure 6. The message informs you that you are not able to create two logons. In a one-to-one relationship, an employee can have only one logon. Duplicate values not allowed Figure 6 Microsoft Access Chapter 2 - Building a Relational Database and Creating Forms More Skills: SKILL 12 Page 5 of 6

6 19. With the Access message still displayed, click Start, and then click All Programs. Click to open the Accessories folder, and then click Snipping Tool. 20. In the displayed Snipping Tool program window, click the New button arrow, and then click Full-screen Snip. 21. Click the Save Snip button. In the Save As dialog box, navigate to your Access Chapter 2 folder. In the File name box, type a02_employee_logons_snip_your_name and then click the Save Snip button. Close the Snipping Tool window. If you do not have the Snipping Tool, which is available in Windows Vista Home Premium edition, press p, and then paste the screen into a Word document. 22. In the displayed Access message, click OK. Press E to cancel adding the second logon. Close the table, and then Exit Access. 23. Print a02_employee_logons_snip_your_name or submit your files electronically as directed by your instructor. You have completed More Skills 12 Microsoft Access Chapter 2 - Building a Relational Database and Creating Forms More Skills: SKILL 12 Page 6 of 6