Transcript Access 2013

Microsoft Office
Microsoft
Access 2013 Office
Access 2013
Courseware # 3255
Lesson 2: Building Tables
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Access 2013
Lesson Objectives
•
Identify the purpose and nature
of tables
•
Plan tables for a database
•
Plan table fields
•
Understand naming conventions
•
Draw a model of a table
•
Understand data types
•
Understand how the Field Size
property affects storage
requirements
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• Create tables in Table Design
view
• Modify field properties and
field descriptions
• Define primary keys
• Modify table structure
• Insert, delete and rename
fields
• Create tables in Datasheet view
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Lesson Objectives
Use Quick Start fields
Use Application Parts
Use User Templates
Enter records in Datasheet
view
• Import data into a new table
• Append records to an existing
table
• Import data as a linked table
•
•
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•
Modify the layout of a
datasheet
•
Create relationships
•
Create lookup fields
•
Add records to related tables
using sub-datasheets
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Table Basics
• A table is a collection
of data about a
specific topic
• The data is organized
into rows and
columns
• Each column is a field
and each row is a
record
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Planning Tables
• A well-planned database
ensures that data is
complete, unique and
accurate
• Be sure to have a clear
picture of how the
database will be used
• Begin by listing the data
you want to capture
• Remember that a table
should store data about
one thing, and only one
thing
– The subject matter
categories that are
generated in your list will
become the tables
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Planning Fields
• Use the smallest fields that
make sense – this allows
you great flexibility for
sorting and searching the
data
• Remember that it is easier
to build in flexibility during
the design stage than it is to
redesign tables after records
have been added or queries
and reports have been
created based on table data
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Naming Rules and Conventions
• A table name can be up to 64 characters long
• A field name can be up to 64 characters long
• Avoid using special characters (punctuation marks,
slashes, backslashes, etc.) in table names, field names or
other object names
• Embedding spaces into a table name or field name can
lead to complications in creating expressions
– Use camel case, or an underscore (_) to represent a space
• Use meaningful names
• Each table within a database must have a unique name
• Each field within a table must have a unique name
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A Model of Table Structure
• The Information Engineering
(IE) model is a standard model
for representing table structure
• In the IE model, a table is
represented by a rectangle
– The name of the table appears
at the top of the rectangle
– Each field is listed beneath the
table name
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Data Types
• The properties of a field describe the characteristics and
behavior of the data entered into that field
• A field’s data type determines the type of data the field
can store
• A field can contain only type of data
• You set the data type for a field in Table Design view
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Data Types – Defining
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Use the upper section of the
Table Design view window to
specify field names, data
types and descriptions
•
The field name and data type
are both required attributes
•
Use the lower section of the
window (the Field Properties
pane) to specify additional
properties
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Data Types in Access 2013
Short Text
Stores up to 255 characters of text, a combination of text and
numbers or numbers that will not be used in calculations
Long Text
Stores a block of text or a combination of text and numbers
(stored as text) longer than 255 characters
Number
Stores a numeric value that is not a monetary value. Use this
type if you will perform calculations on the field
Date/Time
Stores time-based data
Currency
Stores monetary data. Data stored in this type of field is not
rounded off during calculations and the field is accurate up to
15 digits to the left of the decimal point and 4 digits to the right.
AutoNumber
Automatically provides a unique numeric value for anew record
when it is added to a table. This data type is used in ID fields.
Yes/No
Stores True or False values. A field with this data type can
contain only one of two values: Yes/No, True/False or On/Off.
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Data Types in Access 2013
OLE Object
Used to attach an Object Linking and Embedding (OLE) object
to a record. Use the Attachment data type to attach most types
of files that do not require OLE. OLE fields do not allow you to
attach multiple files to a single record.
Hyperlink
Used to store a hyperlink (up to 2048 characters), such as an
e-mail address or a Web site URL.
Attachment
Used to attach multiple files (such as images, sound files, Excel
spreadsheets or Word documents) to a record.
Calculated
Performs calculations on fields within the table. A calculated
field cannot perform calculations that involve fields from other
tables.
Lookup Wizard Displays either a list of values that is retrieved from a table or
query, or a set of values you specify when you create the field.
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Field Size Property
•
Field properties control how a field’s
data is stored, handled or displayed
•
The data type of the field
determines which field properties
are available for that field
•
The Field Size property specifies the
maximum size for a field, and
directly affects the storage and
memory requirements for each
record
•
The Field Size property is accessible
in the Field Properties pane of the
Table Design window
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Field Size Property for a Text Field
• The default field size for a text field is 255 characters
• Specifying a field size for a text field limits the number of
characters that can be stored in the field
– If you know that a field will store only a limited number of
characters, for example, a State field would store only two
letters, change the field size for the State field to 2 to give
users a visual clue of what type of data is expected
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Field Size Property for Number and
AutoNumber Fields
Byte
Stores whole numbers for 0 to 255 in 1 byte of storage
Integer
Stores whole numbers between -32,768 and 32,767 in 2 bytes
of storage
Long Integer
Stores whole numbers between -2,147,483,648 and 2,147,483,647
in 4 bytes of storage
Single
Stores numbers from -3.4 x 10308 to 3.4 x 10308 in 4 bytes of
storage. Allows fractions and provides decimal precision to 7
digits.
Double
Stores numbers from -1.798 x 10308 to 1.798 x 10308 in 8 bytes of
storage. Allows fractions and provides decimal precision to 15
digits.
Replication ID
A 16-byte field used to establish a unique identifier for replication
Decimal
Stores numbers from -9.999 x 1027 to +9.999 x 1027 in 12 bytes
of storage
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Table Views
• Datasheet view – used primarily for working with table
data (although you can create tables in Datasheet view).
This is the “open” view for a table
• Design view – used to create, view or edit a table’s
structure. You cannot see the data in Design view.
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Creating Tables in Design View
• The Table Design view
window has an upper
and lower pane
• Type field names, data
types and an optional
description in the
upper pane
• Set field properties in
the Field Properties
pane (the lower pane)
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Modifying Tables in Design View
• You can use Table Design view to change field names,
change field types and change field properties
• You can also add fields, delete fields, insert fields or
rearrange fields
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Primary Keys
• A primary key is a field (or combination of fields) that
uniquely identifies each record stored in a table
• No two records in a table may be exact duplicates – two
records may, however, contain duplicate data other than
the primary key
• Primary key must be unique
• Primary key cannot contain a null value
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Selecting a Primary Key
• A primary key should be
– A value that will never change
– A value that is extremely unlikely to be null
• Poor choices include: people’s names and social security numbers
• Good choices include unique identifiers issued by an organization or
an ID field
• When you use an ID field as a primary key, you can manually enter
the ID number or you can elect to have Access create ID numbers
automatically by setting the data type to AutoNumber
• To specify a field as a primary key select the field in Table Design
view, then click the Primary Key command button in the Ribbon
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Creating Tables in Datasheet View
• Use the commands on the Fields
tab in the Ribbon when creating
tables in Datasheet view
• Click any command button in the
Add & Delete group to add a field
• Click the More Fields button to
display a list of field types and
formatting options
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Reusing Design Elements
• Access 2013 provides several tools that allow you to use
(and reuse) pre-defined design elements. These include:
– Quick Start fields
– Application parts
• Reusing design elements allows you to create tables and
related database objects quickly and easily.
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Using Quick Start Fields
• Quick Start fields are listed at the
bottom of the More Fields list
• Use Quick Start fields to add
pre-defined fields to a table
• Each Quick Start field is
automatically defined with a
name, data type and formatting
(if applicable)
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Using Application Parts
• Application Parts add
functionality to a database
• An application part may
consist of a single table, or it
can comprise several related
objects such as tables, forms
and queries
• Click the Create tab in the
Ribbon, then click the
Application Parts command
button to view the gallery of
available objects
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Using User Templates
• You can save parts of a database as template objects.
– You can save tables and other objects as user-defined
application parts (*.accdt), and
– You can save selected fields as user-defined data type
templates (*.accft).
• You use a user-defined data type just as you would use a
Quick Start field
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User-Defined Data Type Templates
• To save a user-defined data type
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open a table in Datasheet view
select the fields that you want to save for reuse
click the More Fields button
select Save Selection as New Data Type
• Access saves the new data type template in the following
location:
Users\<Username>\AppData\Roaming\Microsoft\Templates\Access
• Once you create a user-defined data type, you can select
it in the More Fields drop-down list
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User-Defined Application Parts Template
• User-defined application parts templates appear in the User
Templates section at the bottom of the Application Parts
gallery
• To save a database as a template (with or without data)
– Open the database you want to save as a template
– Strip out the objects you do not want to include in the
application part
– Switch to Backstage view
– Click the Save As tab
– In the Save Database As section, select Template (*.accdt)
– Click the Save As command button
– Click the Application Part checkbox
– Identify a primary table if necessary
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Importing Data
• You can import data to:
– A new table
– An existing table
– A linked table
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• You can import data from:
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Access databases
SQL Server databases
Excel spreadsheets
Text files
XML files
HTML documents
Outlook folders
SharePoint lists
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Importing Tables from Other Databases
• Click the External Data tab
• In the Import & Link group, click Access to launch the
Get External Data Wizard
• Specify a source database file
• Select the database objects you want to import
• Click OK
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Importing Data from Excel
• Click the External Data tab
• In the Import & Link group, click Excel to launch the Get
External Data Wizard
• Specify a source database file
• Specify whether you want to:
– Import source data to a new table
– Append a copy of the records to an existing table
– Create a linked table
• Follow the instructions on the remaining wizard screens
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Importing Data to a New Table
• Access creates the new table during the import process
• If a table of the same name already exists, it will be
overwritten
• Imported data is copied from an outside source – it will
not be automatically updated if the source file is updated
• Changing data in the Access table does not affect the
source file
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Appending Records to an Existing Table
• Use the Get External Data wizard
• The append operation does not overwrite data in the
existing table
• The structure and data types in both the source and
destination files must match
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Importing Data as a Linked Table
• Each time the source file is updated, the linked table
automatically reflects the most recent changes
• In most scenarios, linking allows you to add and update
data either in the source file or in the linked table.
Exceptions are as follows:
– When you link to data in a text file, you can add new
records in Access, but not update records
– When you link to an Excel workbook or a Data Services file,
the linked table is a non-updatable recordset. If you want
to add, edit or delete data, you must make the changes in
the source file.
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Working in Datasheet View
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Working with Records – Navigating a Datasheet
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Adding, Updating and Deleting Records
• Use the arrow keys, the Tab key and the mouse to move
from field to field
• As you enter new or revised data into a table record, a
pencil icon displays in the record selector to indicate that
the record contains unsaved changes
• When you reach the end of a record, you can press Tab
or Enter to automatically save the current record and
move the cursor to the next record
• You can also press Ctrl+S to save changes from
anywhere in the datasheet
• You must confirm deletions
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Manipulating a Datasheet
• Size and Position Datasheet Columns
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Hide or Unhide Columns
Resize Fields
Rearrange Fields
Freeze and Unfreeze Fields
• Customize the Appearance of Datasheet Data
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Add table descriptions
Change field captions
Insert total rows
Change data formats
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Printing Datasheet Records
• In Backstage view, click
the Print tab, then
select:
– Quick Print
– Print
– Print Preview
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Constraining Input – Validation Rules
• A validation rule is a criterion that must be met before a
record can be saved
• Enter the criterion in the Validation Rule row in the Data
tab of the Property Sheet
• You can specify optional validation text that will display
as an error message if the validation rule is not met
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Constraining Input – Input Masks
• An input mask is a string of characters that indicates the
format of valid input values for a field
• Input mask has 3 parts:
– First part (mandatory) – includes the mask characters along with
placeholders and literal data such as parentheses, periods and
hyphens.
– Second part (optional) – controls whether the embedded mask
characters are stored within the field. If the second part is set to
0, the characters are stored with the data. If it is set to 1, the
characters are displayed in the field but are not stored as part of
the data.
– Third part (optional) – indicates a single character or space that is
used as a placeholder. By default, Access uses the underscore (_)
character, but you can specify the character you want to use.
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Constraining Input
Default Values
• Specify a default value for a field to speed data entry
• Type the default value in the Default Value row of the
General tab in the Field Properties pane in Table Design
view
Auto-incrementing Fields
• To set a field to auto-increment, set the data type to
AutoNumber
• There can be only one AutoNumber field in a table
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Table Relationships
• A column in a table
that references the
primary key of
another table is
called a foreign key
• Foreign keys and
primary keys
represent data
relationships
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Table Relationships
• A relationship is made by matching data in key fields
between two tables
• When creating relationships, remember:
– Related fields may or may not have the same name but
must have the same data type
– When related fields are Number fields, they must have the
same Field Size property setting
– To define a relationship using an AutoNumber primary key
field, the foreign key must be a Number field with a Field
Size property setting of Long Integer
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Relationship Types
One-to-one
A relationship in which each record in Table A can have only
one matching record in Table B, and vice versa.
One-to-many
Parent-child
A relationship in which 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. The relationship is
established only if the common field is the primary key in
Table A and the foreign key in Table B.
Many-to-many A relationship in which one record in either Table A or Table
B can relate to many matching records in the other table.
Relational databases cannot directly handle many-to-many
relationships, and these must be replaced by multiple oneto-many relationships.
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Representing table relationships
• In an IE diagram, you
represent relationships by
drawing lines between the
key fields
• The “one” side is indicated
by drawing a 1 beside the
parent key
• The “many” side is
indicated by drawing an
infinity symbol (∞) beside
the foreign key
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Creating Relationships in a Database
• Open the Relationships
window
• Add tables
• Drag the primary key field
from the parent table
onto the foreign key field
in the related table to
open the Edit
Relationships dialog box
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Table Relationships – Join Properties
• Option 1 is an INNER join.
This is the default join
type – it includes rows
where the joined fields
are equal
• Option 2 is a LEFT OUTER
join
• Option 3 is a RIGHT
OUTER join
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Table Relationships – Join Properties
• Option 1 is an INNER join.
This is the default join
type – it includes rows
where the joined fields
are equal
• Option 2 is a LEFT OUTER
join
• Option 3 is a RIGHT
OUTER join
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When referential integrity is enforced …
• You cannot add a record to a related table unless a
matching record already exists in the parent table
• You cannot change the value of the primary key in the
parent table if matching records exist in a related table
• You cannot delete a record from a parent table if
matching records exist in a related table
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Creating Lookup Fields
• Lookup fields create relationships within a database
• A lookup field in a child table displays values stored in
the parent table
• Use the Lookup Wizard to create a lookup field – the
Lookup Wizard writes a SQL statement to display values
in the lookup field
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Viewing Related Data
• When you define relationships, you can see related data
in a sub-datasheet in Datasheet view
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Lesson Summary
• Create tables in Table Design
view
• Modify field properties and
field descriptions
• Define primary keys
• Modify table structure
• Insert, delete and rename
fields
• Create tables in Datasheet view
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• Identify the purpose and
nature of tables
• Plan tables for a database
• Plan table fields
• Understand naming
conventions
• Draw a model of a table
• Understand data types
• Understand how the Field Size
property affects storage
requirements
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Lesson Summary
•
Modify the layout of a
datasheet
•
Create relationships
•
Create lookup fields
•
Add records to related tables
using sub-datasheets
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Use Quick Start fields
Use Application Parts
Use User Templates
Enter records in Datasheet
view
• Import data into a new table
• Append records to an existing
table
• Import data as a linked table
•
•
•
•
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Review Questions
1.
For a relationship between fields in two tables to be created, the
fields must:
a. have the same data type.
b. have the same name.
c. be stored in separate databases.
d. be defined as lookup fields.
2.
Which of the following is the smallest Field Size setting that will
allow a number field to store the value 1,452,137.5?
a. Integer
b. Long Integer
c. Single
d. Double
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Review Questions
3.
What is the default Field Size setting for a Short Text field in
Access?
a. 12
b. Single
c. Double
d. 255
4.
A primary key:
a. should use social security numbers whenever possible
b. cannot be a composite key.
c. should be null whenever possible.
d. should be a value that will never change.
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Review Questions
5.
Kevin needs to update a field in a table that is linked to data in an
Excel workbook. He should:
a. delete the source data file so that it does not interfere with the
linked table.
b. adjust the value directly in the linked table.
c. adjust the value in the source data file.
d. run the linked table update manager.
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