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Award Sportswear
Database Example
Presenter: Jolanta Soltis
MCSE, MCT, A+
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Planning a database
Gather information on the purpose of the database
–
Interview a range of employees
•
•
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Information on each customer’s payment record
Records of which products a particular customer will
order
Create flowcharts
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Creating Tables
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Creating Tables continued
Structure
Data Types
Field Properties
Primary Key
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Creating Tables continued
Decide what to create
–
–
–
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Customers
Orders
Products
Payment
Modify table in DesignView
– Structure
– Data Type
– Field Properties
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Creating Tables continued
Determine fields for each table
– Id field for each table to serve as a primary key
• Products: ProductID,ProductName, SupplierID,
CategoryID, QuantityPerUnit, UnitPrice, UnitsInStock,
UnitsOnOrder, ReorderLevel, Discontinued
• Orders: OrderID, CustomerID, EmployeeID, OrderDate,
RequireDate, ShippedDate, ShipVia,
• Customers: CustomerID, CompanyName, ContactName,
ContactTitle, Address, City, State, PostalCode,
ProductDescription
• Order Details: OrderID, ProductID, UnitPrice, Quantity,
Discount
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Table Fields
Products:
–
–
–
–
–
–
ProductID – AutoNumber - (primary key)
ProductName – text
ProductDescription – text
UnitPrice – Currency
UnitsInStock – Number
UnitsOnOrder – Number
Finish all tables field properties
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Data Integrity
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Data Integrity continued
Data integrity refers to the accuracy of the data in the database,
for example, the data should accurately portray the real world
– Goal is 100% accuracy
Data integrity problems in databases are often a consequence
of data entry errors
MS Access support the concept of Data Integrity with the
following
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–
–
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Validation Rules
Input masks
Implementation of the formal concept of Referential Integrity
Field Type Checks & Indexes
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Designing Validation Rules for
Database Integrity
A Validation Rule is a rule you design into a DBMS
such that the data entered by a user must precisely
satisfy the rule you establish
– MS Access will prevent a user from entering data that
does not follow your rules, and will display the
validation text you prescribed for the rule the user
violated
Validation rules can not guarantee 100% database
integrity for data entry, but they will help correct many
database entry errors
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Some Validation Rules Within
the MS Access DBMS
Required Fields user cannot leave this field blank
Range of Values value entered must be within a
particular range
Default Values
Legal Values you specify what the legal values are
permitted in data entry for a particular attribute
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Validation Rule 1: To Specify a
Required Field Which Cannot Be
Left Blank on Data Entry
Concept: In Relational Database Design, the attribute(s)
which is (are) the primary key should not be "null" for any
entity record
– With other (non-key) attributes, we may or may not be willing
to accept "nulls" as attribute values
Concept: Mapping With Access:
1.
2.
3.
4.
In Design View, select Field (if not, click on the field-indicator
column)
In Field Properties, click Required
Click Drop-down Arrow
Select Yes (or, alternatively, just delete the default No and enter
Yes)
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Validation Rule 2: To Specify a
Valid Range of Values for an
Attribute in MS Access
1. Select the attribute to apply Validation Rule
2. In Field Properties, click Validation Rule.
3. Enter the appropriate validation expression which expresses
the acceptable values for the attribute, such as:
– >18000
– = 0 And <=90000
– <#1/15/96#
– <[AccountBalance]
• { Alternatively, clicking in the Validation Rule Box and then
clicking the Build button ( ...) brings you into the Access
Expression Builder.}
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Validation Rule 3: Specifying a
Default Value for an Attribute
In Design View, select Attribute
In Field Properties, click Default Value box, which
initially is given a default value of 0 (zero)
Enter default value to apply to attribute if the users
skips over this attribute
This default value applies only to new records, and
not to existing records
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Validation Rule 4: Specifying a
Collection of Legal Values for an
Attribute
In Design View, select attribute to apply the collection
of legal values
In Field Properties, click Validation Rule box.
Enter each legal value in quotation marks ,
separating each legal value by the word Or, i.e.,
= "JAN" Or "FEB" Or "MAR"
Then click Validation Text box, and enter the
message the user should see if the value they enter
is not one of the legal values you defined
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Addendum to Validation Rule 4:
Permitting a Null Value as a
Legal Value
When you specify a collection of legal values, the
input must match one of the legal values
A null value will not normally match the collection of
legal values
To permit a null value as a legal value, add, Or is Null
(without the quotes) to the Validation Rule
– Example: "NY" Or "NJ" Or Is Null
Also note that validation rules are not case sensitive
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Lookup Wizard
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Lookup Wizard continued
Provides a list of values you can choose from when
entering data, making data entry easier and ensures
consistency of data in that field
A Lookup field can get a list of values from a table or
query or from a fixed set of values that you have specified
Enables you to display a list of values in a field in
Datasheet view
– Lookup list field looks up its values from an existing table or
query or another field in its own table
– Value list field displays a fixed set of values that you specify
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Lookup Wizard continued
In Design view click on the Data Type cell of the field that
needs to display the Lookup list or on the menu bar
choose Lookup Column
The name of the foreign key appears in the Field Name
column (The foreign key is the primary key of the table
form which the values come)
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Lookup Wizard continued
To change the properties of Lookup field, from Field
Properties tab, click Lookup tab
– Column heads set to yes will display headings
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Exercise
Create Value List by using Lookup Wizard
– In the number of columns type 2 to specify two
columns for your value list
– In the first column type:
• 5789
– In the second column type:
• 10 14 21 7
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Exercise continued
On the next page choose a column that contains
values that you’d like to store in the database for later
use
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Exercise continued
On the final page type a label for the lookup column:
Employee
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Exercise continued
Final Result is the cell always displays only the value of
the first column of the row you select
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Input Mask Wizard
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Input Mask Wizard continued
Field template that uses literal display characters that
control how data is entered in a field
Used to control the format in which the user enters
values
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Input Mask Wizard continued
1. Open table in Design View
2. Click on Input Mask Properties
3. Follow Wizard Instructions
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Relationships
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Relationships continued
When you create a relationship between tables the
related fields do not have to have the same name,
but they must have the same data type unless the
Primary Key field is an AutoNumber field
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Relationships continued
NAME
EMPID
SALARY
Employee
Employee (EMPID, Name, Salary)
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Relationships continued
YEAR
AUTOID
COLOR
Auto
AUTO (autoid, year, color)
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Representing a Has-a
Relationship
1:1 and 1:N relationships are transformed into a
relational design by creating foreign keys
A foreign key is when you take the primary key from
one table (on the one-side) and place it into another
table (on the many-side) or into the other table for a
1:1 relationship)
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Transforming 1:1 Relationships
Employee
1:1
Auto
EMPLOYEE( EmpNum, Name, Phone, ...)
AUTO( AutoId, Model, Year, Color, ..., EmpNum) or
EMPLOYEE( EmpNum, Name, Phone,..., AutoID)
AUTO( AutoID, Model, Year, Color,...)
–
In both cases, we would want to enforce referential integrity by requiring that the value
of a foreign key in one relation/table appear as the value of a primary key in the other
relation/table.
The Foreign Key can go on either side but, it can be on one side
only
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Questionable 1:1 Mandatory
Relationships
EMPLOYEE
1:1
SS#
1:1 mandatory relationships should be looked at very
closely – sometimes they can be combined into a
single relation/table
However, sometimes it can be justified NOT to
combine the two tables in a 1:1 mandatory
relationship into a single table
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When Not to Combine 1:1
Mandatory Relationships
EMPLOYEE
1:1
JOB-EVALUATION
For Performance, if Job-Evaluation data are
lengthy and used very infrequently
For Security, if Job-Evaluation data needs to be
protected against unauthorized access
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When Not to Combine 1:1
Mandatory Relationships continued
EMPLOYEE
1:1
JOB-EVALUATION
Notice that the relationship here is mandatory in both
directions
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Transforming One to Many
Relationships
Dormitory
1:N
Student
Dormitory ( DormitoryName, Location, NumRooms)
Student ( StudentId, StuName, ..., DormitoryName)
Transformation Rule: The Primary Key of the entity set on
the One side of the relationship becomes a foreign key of
the entity set on the many side of the relationship
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Representing 1:N Relationships
In each of the following examples, the foreign key goes to
the right (into the many-side)
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Data Structure Diagrams
ProfessorName goes into the Student table as a Foreign
Key
Note - that in a DSD, a crow’s foot on a relationship
line indicates a many relationship
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Transforming Many to Many
Relationships
Student
M:N
Class
Student( StudentNum, StuName, Phone, ...)
Class( ClassNum, ClassName, ...)
Stu-class( StudentNum, ClassNum)
Rule: Create a new relation, called an Intersection relation,
whose only (***unless there is also an attribute belonging to the
relationship***) attributes will be a composite primary key
consisting of the primary keys of the participants in the
relationship.
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Representing a M:N Relationship
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Representing a M:N Relationship
continued
A one-to-many relationship is the most common type
of relationship
A record in Table A can have many matching records
in Table B, but a record in Table B has only one
matching record in Table A
– One supplier, can supply more than one product, but
each product has only one supplier
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Representing a M:N Relationship
continued
In a many-to-many relationship, a record in Table A
can have many matching records in Table B, and a
record in Table B can have many matching records in
Table A
This type of relationship is only possible by defining a
third table (called a junction table) whose primary key
consists of two fields — the foreign keys from both
Tables A and B
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Representing a M:N Relationship
continued
A many-to-many relationship is really two one-tomany relationships with a third table
– For example, the Orders table and the Products table
have a many-to-many relationship that's defined by
creating two one-to-many relationships to the Order
Details table. One order can have many products, and
each product can appear on many orders
In a one-to-one relationship, each record in Table A
can have only one matching record in Table B, and
each record in Table B can have only one matching
record in Table A
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Representing a M:N Relationship
continued
This type of relationship is not common, because
most information related in this way would be in one
table
You might use a one-to-one relationship to divide a
table with many fields, to isolate part of a table for
security reasons, or to store information that applies
only to a subset of the main table
– For example, you might want to create a table to track
employees participating in a fundraising soccer game.
Each soccer player in the Soccer Players table has
one matching record in the Employees table
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Referential Integrity
Referential integrity is a system of rules that Microsoft
Access uses to ensure that relationships between
records in related tables are valid, and that you don't
accidentally delete or change related data. You can
set referential integrity when all three conditions are
met:
1. The matching field from the primary table is a primary
key or has a unique index
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Referential Integrity continued
2. The related fields have the same data type. There are
two exceptions. An AutoNumber field can be related
to a Number field with a FieldSize property setting of
Long Integer, and an AutoNumber field with a
FieldSize property setting of Replication ID can be
related to a Number field with a FieldSize property
setting of Replication ID
3. Both tables belong to the same Microsoft Access
database. If the tables are linked tables, they must be
tables in Microsoft Access format, and you must open
the database in which they are stored to set
referential integrity. Referential integrity can't be
enforced for linked tables from databases in other
formats
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Relationship
The employee sells to the customer
The customer orders a product
The order contains a number of order details
Relationships from the central table (Orders)
–
–
Each order is placed by a single customer
One customer can place several orders
Customer
Orders
One-to-many
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Relationship continued
Some orders are paid off in installments
Each installment is for a single order
Orders
Payment
One-to-many
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Relationship continued
Several different products can be ordered in a single
order.
Each product can be ordered many times
Products
Customer
many-to-many
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Relationship continued
In order to create a many-to-many relationship
between Orders and Product, you create a junction
table – Order Details
The primary keys of both the Orders and the
Products table are included in the Order Details
primary key. Order Details is the Junction Table
Products
Orders
many-to-many
Order Details
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Relationship continued
In the Relationship window you drag the OrderID in
the Order table to the ProductID in the Order Details
junction table
Drag the ProductID from Products table to ProductID
in the OrderDetails table
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Relationship continued
Many-to-many relationship
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Queries
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Queries continued
Allow you to retrieve the information stored in tables
in a variety of ways
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Criteria for creating Queries
Wildcards and Mathematical Expressions:
– Comparison Operators
= (Equals)
> (Greater than)
< (Less than)
>= (Grater than or equal to)
<= (Less than or equal to )
<> (Not equal to )
Between (ex. Between 1 And 1000)
In (In [ “NY” , “CA” , “NJ” ] means “is member of a list"
Is Null (There is no value entered in the field)
Is Not Null (There is a value entered in the field)
Like (Like “smi*” means “has a string ‘smi’ at the beginni9ng of
the field”)
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Criteria for creating Queries
continued
– Logical Operators:
And ( “>0 and <=10” )
Or ( “<-2 or >2” )
Not (Not Like “smi*” means “the field does not start
with “smi*”)
– Wildcards
? Any single character, ex. BL-3435
* Any string of characters, ex. Por*
# Any number, ex. 46#7
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Criteria for creating Queries
continued
Examples
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–
–
>”01/01/95”
Like “S*” Or Like “A*”
Like “1/?/01”
Where [BirthDate] >= #1/1/60#
Between 1 And 5
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Simple Query
Allows you to bring together related information that
are stored in different areas
Review from last week
– Create Query based on: Customers, OrderDetails,
Orders
Click on Total button
From Group By choose :Sum for Quantity and Avg
for Unit Price
Run the Query
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Simple Query continued
In the empty column type
Amount: CCur ([UnitPrice]*[Quantity]
Name of New
Column
Currency
In the Criteria type:
[Enter the State code]
Query will ask you for the state name
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Query in Datasheet View
In the Datasheet view below are listed the main ways
to apply a filter to a query’s record set:
– By selection (quick, using a single criterion)
– Filter excluding selection (to extract all records that
don’t contain a particular value
– By form (more than one criterion)
– Using advanced filtering or sorting options
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Totals and Parameter Query
Total query performs calculation on groups of data
Parameter query performs calculation on groups of
data – dialog box that prompts you for criteria each
time you run the query
Create query in Design View
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Totals and Parameter Query
continued
To define a totals query, you need to click the Total
button to display the Total row in the design grid.
By default, Group By appears in the Total row
– By selecting Where and specifying criteria you can
filter data
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Exercise
Create a totals query that calculates how many units of
each of your company’s product are on order
– Create select query with:
• Product Name from table Products
• Quantity from table Order Details
– Click on Sum button
• Quantity field - Group By: Sum
– Run the query
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Parameter Query
To create, in the Criteria Field, Type a customer
name: enter a value in enclosed brackets []
You can designate several fields as parameters:
Type the first date: between Type a product name:
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Exercise continued
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Exercise continued
Create a parameter query to view order details for a
particular product during a certain period
– Create query with field you need:
•
•
•
•
•
OrderDate from Orders
CompanyName from Customers
ProductName from Products
UnitPrice from OrderDetails
Quantity from OrderDetails
– Click on Criteria in the OrderDate field
– Type: Between [Type the first date:] And [Type the second
date:]
– Click on the Criteria in the ProductName field
– Type: [Type a product name:]
– Run the query
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Exercise continued
Final Output
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Action query
Allows you to change and add amounts of data
quickly and accurately
Four types:
– Make-table allows you to create a new table from data
in one or more existing tables
• Allows to combine the fields you want in a new table and
export the table to another database
– Append allows you to insert records from the table in
one database to a table in another database
– Update
– Delete
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Make-Table Query continued
Make a table using the fields in your select
query: Product Order Details Query
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Make-Table Query continued
Change Query type to Make-Table Query
Type Customer Order Details as title
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Append Queries
Two databases: “AwardInventory” and “AwardCustomer”
(both have Products table)
There are more records in the AwardInventory Products
table than in its equivalent in the AvardCustomer
You need to link them:
– Open AvardCustomer
– File – Get External Data – Link Tables
– Point to AvardInventory
Create a select query, choose fields
From Query menu choose Append Query…
The Show row in the Query Design window changes to
Append To and indicates the fields to which records will
be appended.
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Update Query
To update records
Create a select query, add fields
Go to Query – Update Query
In the Update To row type an expression to update
– Ex. Unit price field: type [UnitPrice]*1.1 to increase
prices
– Criteria: type Printed
– Run the query
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Delete Query
To remove records
Create select query
Add Products table
To specify the table from which records will be
deleted, you drag the asterisk(*) from the Products
table to the Field row in the Query Design grid
Drag the filled you want to set criteria into the next
column
– Ex. Product Description: type Blank
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Queries and Join Properties
Access can join tables on fields not present in
table relationships as long as they have the
same data type: Auto Number, Number
Types of Joins
– Inner join: This is the most common of joins. It returns
only those records from both tables where there is a
matching value in the related fields (usually the primary
and foreign key values).
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Queries and Join Properties
continued
– Outer joins (can be either a Left or a Right Outer Join) tell a
query that although some of the rows on both sides of the
join correspond exactly, the query should include all of the
rows from one table, and also those rows from the other
table that share a common value on both sides of the join
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Practice
Summary of orders placed per customer
whether they placed order or not.
Tables:
– Customers (CustomerID, CompanyName), Orders
(Order Date) (related by CustomerID filed)
– Create a query
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Indexes
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Indexes continued
To optimize a query’s performance, Index the fields
that are most frequently queried, when searching,
Access looks up data’s location in the index
– The primary key of a table is automatically indexed
– Index foreign keys as well
Consider indexing a field if it meets the following
criteria:
–
–
–
–
You anticipate searching for values stored in the field
You anticipate sorting values in the field
You anticipate storing many different values in the field
Field’s data type is Text, Memo, Number, Date/Time,
AutoNumber, Currency, Yes/No or Hyperlink
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Indexes continued
Open Employees table in Design View
Click on Indexes button
– Type: Name
– Choose FirstName
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Performance Analyzer
Switch to the Database window
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Performance Analyzer continued
Allows you to analyze a query
– From Tools menu, click Analyze
– Click Performance
– Then select Queries
The Performance Analyzer gives you all suggestions
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Forms
Used to capture information into tables
Create:
–
Customer Capture Form
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Reports
Allow you to view and print information from tables
Create:
–
Customer’s Payments
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Pages
Used to view data access pages from internet
Create
–
Products
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Macros
Used to automate common tasks involving one or
more actions, such as printing a report
Crate
– Print Payments
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Modules
Construct using Visual Basic for Applications. This
provides added functionality to databases
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If you have any questions, please feel free to
contact Academic Computing Services
Jolanta Soltis
IT Consultant
(973) 596-2925
e-mail [email protected]
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