Microsoft Access Lesson 3 Lexington Technology Center February 18, 2003 Bob Herring On the Web at www.lexington1.net/AdultEd/computer/microsoft_access.htm

Review of Thursday’s Lesson Access Lesson 3 Review of Thursday’s Lesson Template Databases Database Wizard Switchboard Forms Forms and Controls Reports Database Window 2

Access Lesson 3 Relationships Tables can be related if they have a field in common. Access uses the relationship to create information by matching the fields and reporting the results. There are 3 types of relationships: One-to-many: Each record in the primary table can be associated with many records in the related table One-to-one: Each record in the primary table can be associated with only one record in the related table Many-to-many: More than one record in the primary table can be associated with many records in the related table 3

Relationships in Access Access Lesson 3 Relationships in Access The table on the “one” side of the relationship is called the parent table. The other table is called the child table. How the 3 types of relationships are created in Access: One-to-many: The common field in the parent table is called the primary key, and the related field in the child table is called the foreign key. One-to-one: The common fields are both primary keys. Many-to-many: Ordinarily not possible, but in Access two one-to- many relationships can be joined to create this kind of relationship. 4

One-to-Many Relationships Access Lesson 3 One-to-Many Relationships In this example, one category can encompass many products Child Table Foreign Key Parent Table Primary Key Relationship Line 5

One-to-One Relationships Access Lesson 3 One-to-One Relationships These two tables have a one-to-one relationship because they concern the same subject: employees 6

Many-to-Many Relationships Access Lesson 3 Many-to-Many Relationships Since many orders might call for many products, a junction table is used to avoid violating referential integrity. Junction Table 7

Referential Integrity Access Lesson 3 Referential Integrity Optional series of rules that guarantees that relationships will be valid. Every record in a child table (the “many” side) must have one and only one record in the parent table (the “one” side) No child record can be entered without a parent No parent record can be deleted if it still has children No child record’s foreign key can be changed without a match in the parent table No parent table’s primary key can be changed if there are child records 8

Referential Integrity, Continued Access Lesson 3 Referential Integrity, Continued What you need to enforce referential integrity in Access: The matching field in the parent table must be the primary key Relating fields must be the same data type Both tables must be in the same database -- OR, if using linking fields, both tables must be in Access and the linked table’s database must be open Referential integrity is indicated by 1 -  on the relationship line Referential Integrity Enforced 9

Referential Integrity, Continued Access Lesson 3 Referential Integrity, Continued Referential integrity is set by editing the relationship Right-click the relationship line and select Edit Relationship Click the “Enforce Referential Integrity” check box Enforce Referential Integrity Edit Relationship 10

Referential Integrity, Continued Access Lesson 3 Referential Integrity, Continued If referential integrity is selected, you can also choose to have Access automatically update or delete records Cascade Update and Cascade Delete maintain referential integrity by changing child tables to match changes in the parent table Beware of Cascade Delete!! This could lead to loss of data! Cascade Update has no effect if you are using a primary key since you cannot change an autonumber Cascade Update Cascade Delete 11

Access Lesson 3 Joins A join is a control that tells Access which records to select when running a query. Inner joins are the most common. Outer joins include all records from one of the tables and records from the other when the joined fields match. Left Right Inner Join Left Outer Join Right Outer Join 12

Address Book Relationships Access Lesson 3 Address Book Relationships 13

Asset Tracking Relationships Access Lesson 3 Asset Tracking Relationships 14

Contact Management Relationships Access Lesson 3 Contact Management Relationships 15

Event Management Relationships Access Lesson 3 Event Management Relationships 16

Expenses Relationships Access Lesson 3 Expenses Relationships 17

Students and Classes Relationships Access Lesson 3 Students and Classes Relationships 18

Inventory Control Relationships Access Lesson 3 Inventory Control Relationships 19

Access Lesson 3 Ledger Relationships 20

Resource Scheduling Relationships Access Lesson 3 Resource Scheduling Relationships 21

Time and Billing Relationships Access Lesson 3 Time and Billing Relationships 22

Membership Relationships Access Lesson 3 Membership Relationships 23

Order Entry Relationships Access Lesson 3 Order Entry Relationships 24

Book Collection Relationships Access Lesson 3 Book Collection Relationships 25

Music Collection Relationships Access Lesson 3 Music Collection Relationships 26

Access Lesson 3 Form Wizard In the Northwind database, select the “Forms” tab Click the “New” button 27

Access Lesson 3 Form Wizard In the “New Form” dialog box, click “Form Wizard” Choose the Products table to begin, then click “OK” 28

Wizard, Step 2 -- Data Fields Access Lesson 3 Wizard, Step 2 -- Data Fields Step 2 is to choose fields from the available tables and queries Click the right arrow to select the desired fields, or Click the double right arrow to select all 29

Choosing Fields for a Form Access Lesson 3 Choosing Fields for a Form Select “ProductName”, “SupplierID”, “UnitsinStock”, and “Discontinued” Choose “Next” 30

Wizard, Step 3 -- Layout Style Access Lesson 3 Wizard, Step 3 -- Layout Style In Step 3, select a layout style for the form Click through the four choices to preview the different styles Click “Next” Columnar Tabular 31

Wizard, Step 3 -- Layout Style Access Lesson 3 Wizard, Step 3 -- Layout Style In Step 3, select a layout style for the form Click through the four choices to preview the different styles Click Next Datasheet Justified 32

Wizard, Step 4 -- Background Style Access Lesson 3 Wizard, Step 4 -- Background Style In Step 4, select a background style for the form Click through the choices to preview the different styles 33

Access Lesson 3 Wizard, Step 5 -- Finish To finish the form, give it a name and click “Finish” Click the radio button to open the form after creating it Open the Form 34

Automatic Form in Action Access Lesson 3 Automatic Form in Action The new form displays a portion of the information in the table Forms are two-way -- they display information, but also guide data entry 35

Access Lesson 3 Adding a New Product Click the “New Record” button Notice that the “Supplier” field is lit -- this is referential integrity in action -- every product must have a supplier! 36

Access Lesson 3 Adding a New Product After choosing a supplier, enter the name of the new product Enter the number of units in stock Data entered in the form is immediately saved in the database 37

Access Lesson 3 Review Relationships Referential Integrity Joins Template Database Relationships Automatic Forms 38