1. Microsoft Access Validation Rules, Table Relationships And
Action Queries

2. Objectives Understand and use data validation
Establish table level relationships
Define and create an action query

3. Part One
Validation Rules

4. Validation Rules and Text
Property is an object characteristic that defines how that object will look and behave
Validation properties maintain data integrity
Reduce errors
Simplify the entry process
Two validation properties in Access
Validation Rule
Validation Text

5. Validation Rules and Text
Validation Rule property
Rejects a record when data is entered that does not agree to the rules as set out in this property
Validation Text property
Provides the user with a message that tells them how the data should be entered
Validation Text is not required when using Validation Rule, however strongly recommended

6. Change Field properties
Switch to Design View
Format property:
@: text character or space is required Example: displays as
> : force upper case characters
< : force lower case characters
&: text character is optional
Example: four out five characters are required and the 5th is optional (12-34 or )

7. Change Field properties …
Default Value property:
Enables automatic insert of a field value when a new record is created
Input Mask:
Controls how data is entered in the field
Example: (000)000-AAAA would accept a combination of numbers (first six) and characters (last four).
The display would be: (___)___-_____
Validation Rule:
Limits what the user can enter in the field.
Example: > 0 And < 9 would limit the display to numbers in this range (between 0 and 9).

8. Default Value
property
Format Property

9. Validation Rule Examples
Symbol
Example
Meaning
<>
<>50
Value entered must not be 50
Like
Like “Jones”
Value entered must be Jones
And
>5 and <15
Value entered must be greater than 5 and less than 15 Or
“B” or “R”
Value entered must be either B or R
Not
Not “Red”
Value entered must not be Red *
Like A*
Value entered must begin with the letter A ?
Like Mi??le
Value must begin with Mi, end with le, and have two characters in the middle =
=10
Value entered must equal 10

10. Example of Input Mask Example Meaning Must enter digit 9
Must enter digit 9
Must enter a digit or space L
Must enter letter ?
May enter letter A
Must enter letter or text a
May enter letter or text
&
Must enter any character or a space C
May enter any character or a spase

11. Relationships and Referential Integrity
Part Two

12. Relationships
Connecting fields with like information, or physically joining two (or more) tables
In the Relationship window
Relationship is at the table level
When queries are created
Relationship is at the query level
Table level relationships take precedence over query level relationships

13. Table-level Relationships
The Relationships window used to define, view and edit table relationships
When properly designed, every table in a database is related to at least one other table in the database
A table may be related to more than one other table
Important to know which will be the “parent” table and which will be the “child” table in the relationship

14. Table-level Relationships
Parent
In a one-to-many relationship the “parent” is the “one” in the relationship
Referred to as the primary table
Child
In a one-to-many relationship the “child” is the “many” in the relationship
These definitions also apply to query level relationships

15. Relationships Four types of relationships One-to-one Rarely used
One record in a table has one record in another table
One-to-many
One record in a table has many records in another table
Many-to-one
Also known as lookup table relationship
Many records in a table have one record in another table

16. Relationships Many-to-many Most difficult of all relationships
Needs a new table especially created for the relationships, junction table
May be thought of as par of one-to-many relationships between two tables
Many records in a table have many records in another table

17. Forming Relationships
Primary Key
Most often the field chosen when defining a relationship
Joined fields should be the same name, must be the same data type
Once a primary key is selected, Access prevents any duplicate or Null values from being entered in the primary key fields
Foreign Key
One or more table fields that refer to the primary key field in the primary table
Indicates how the tables are related

18. Relationships Window CustomerID is primary key Join line
in Customers table
Join line
Enforce Referential
Integrity
CustomerID is
foreign key in
Loans table

19. Referential Integrity
Rules that help to maintain accuracy between tables
Parent-child relationship exists between linked tables
First table is the parent
Table the parent is linked to is the child
Establishing referential integrity prevents the creation of an orphan
Ensures related tables are consistent with one another

20. Referential Integrity
Parent
Child
This is a one-to-many relationship
Notice the number “1” by the parent relationship line
Notice the “∞” by the child

21. Referential Integrity Rules
Primary record (parent key) must exist before the child may use that key
Parent record cannot be deleted if it still has “child” records
Parent table field that is linked to the child cannot have its value or data changed so long as it has children

22. Referential Integrity
Cascade Update:
When selected any changes made to the key value of the primary table will be applied to records in the related tables
For example, if “Customer ID” is the primary key in the parent table, and is the foreign key in the child table, then any changes made to the Customer ID in the parent table will be automatically reflected in the child table

23. Referential Integrity
Cascade Delete:
When selected related records will be deleted when the primary record is deleted

24. Multiple-Table Queries
One-to-many relationship
Primary key
Foreign key
Referential integrity
Word Wrap - text automatically wraps text from one line to the next without pressing the enter key
Hard Return - created by the user when the enter key is pressed
Soft Return - created by the word processor as it wraps text from one line to the next
Insertion Point - Flashing vertical line that marks the place where text will be entered
Toggle Switch - A switch that causes the computer to alternate between two modes. For example, Caps Lock alternates between uppercase and lower case.
Insert Mode - Moves existing text to the right as new characters are being added. Insert key toggles between insert and overtype mode.,
Overtype Mode - Types over existing characters as new characters are added. Used for correcting typos.
Normal View - this view shows the only the body of the current page; faster and preferable when entering text and editing (See Figure 1.6 page 15 in textbook)
Page Layout View - this view shows the complete page with headers, footers and all formatting applied (See Figure 1.7 page 16 in textbook)
AutoCorrect Feature - corrects predefined spelling errors and/or mistakes in capitalization, automatically as the words are entered.

25. Multiple Table Query Primary key in Consultants Table Relationship
between tables
(one to many)
Foreign key in Clients Table
Each field &
table to display