Exploring Microsoft Access Chapter 5 One-to-Many Relationships: Subforms and Multiple Table Queries.
-
Upload
rebecca-hunter -
Category
Documents
-
view
225 -
download
0
description
Transcript of Exploring Microsoft Access Chapter 5 One-to-Many Relationships: Subforms and Multiple Table Queries.
Exploring Microsoft Access
Chapter 5One-to-Many Relationships:
Subforms and Multiple Table Queries
• One-to-many relationship essential in database design
• Use the Relationships window
• Define referential integrity
Objectives (1 of 2)
• Distinguish between a main form and a subform
• Create a query based on multiple tables
• Create a main form with two subforms
Objectives (2 of 2)
Overview (1 of 2)• The real power of Access: one-to-many
relationships between tables
• Primary key of one table is foreign key of the related table
• Referential integrity ensures consistency between tables
• Main forms and subforms created from related tables.
• Reports based on a multiple-table query
Overview (2 of 2)
Relationships WindowCustomerID is primary keyin Customers table
Relationship line
CustomerID is foreign key in Loans table
Enforce ReferentialIntegrity
Referential Integrity (1 of 2)
• Access automatically implements a form of data validation during data entry
• Can enter a record in the “one” table, but not in the “many” table if record contains an invalid value for the foreign key
• This ensures related tables are consistent with one another.
Referential Integrity (2 of 2)Delete Record button
Click + to displayrelated records(subdatasheet)
Cannot delete a Customer without first deleting related Loan
Subforms
• Subform is a form within a form
• Main form would be based on primary table, while subform is based on related table
• Use Subform Wizard
• Can be created either on main form or dragged from a separate form
Form Wizard (1 of 4)
Select the tableor query forthe form
Select all fieldsto add to the form
Step 1
Step 2
Form Wizard (2 of 4)
Step 3
Select the tableor query forthe subform
Select all fieldsto add to the subform
Form Wizard (3 of 4)
Step 4
Step 5
Choose how to displaythe form and subform
Form Wizard (4 of 4)
Choose the style
Enter a name for the form and the subform
Step 6
Step 7
Subform
CustomerC01
Loans forCustomer C01
Status bar forLoans form Status bar for Customers form
Multiple Table Queries
• Query information from two tables
• Create a select query using both tables
• Query window displays selected fields of each table
Multiple Table Queries
Column selector
Enter criteria
Select table
Multiple Subforms (1 of 2)
• A main table can have multiple levels of subforms
• Useful for displaying a one-to-many relationship within a one-to-many relationship
Multiple Subforms (2 of 2)
Customer C01
Loan L031 forCustomer C01
Payments forLoan L031
Chapter 5 Summary (1 of 2)
• Access database may contain multiple tables• Each table has a primary key which is the foreign
key of a related table• Relationships window to create one-to-many
relationships• Referential integrity ensures consistency between
related tables
Chapter 5 Summary (2 of 2)
• Subform is a form within a form• A main form can have multiple subforms• Select query can include fields from several
tables• Tables can be added at any time without
disturbing existing data