This document provides an overview of key concepts for designing and working with relational databases, including: - Databases store related data in tables, with common values creating relationships between tables. - Tables contain records made up of related fields, and proper planning is needed to determine what data to include. - Fields should be short but descriptive, and setting data types controls what values can be entered. - Relationships can be one-to-one, one-to-many, or many-to-many, and referential integrity ensures consistency. - Queries can look up related data automatically across tables.

1. Test 1 Review
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2. Database
 Collection of related data and tools to use, manage
data
 Relational database
 Data stored in tables
 Each table stores data about one thing
 Common values create connections (relationships)
between tables
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3. Fields, Records, and Tables
 Fields
 Basic unit of data represented by a column in a table
datasheet
 Records
 Group of related fields or all fields related to a specific
item: person, place, or thing
 Each row of a datasheet represent a record
 Tables
 Group of related records
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4. Planning a Database
 What information do you want to obtain?
 What data elements (fields) must you include to be able to get
the information?
 What types of data will you enter into each field?
 Dates, numeric values, amounts of money, text, etc.
 What fields of data relate to the same basic items and belong
grouped together?
 How do the groups of data relate to each other?
 What questions will you need the database to be able to answer?
 What is the most efficient way to get data into the database
tables?
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5. Creating Tables
 Each table should contain fields that focus on data
specific to one type of item
 Such as customers, employees, inventory, etc.
 Each table should have a primary key
 Fields in the primary key cannot be empty (null)
 May be one or more fields
 Each generic field# heading is replaced with a
descriptive field name
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6. Table Design Guidelines
 Store all necessary data
 Store data in smallest parts
 Avoid calculations
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7. Using Table Design View
 Presents a blank work area on which to enter
fields
 Provides tools for setting data
types, descriptions, and properties
 Enables you to change the structure and
organization of fields in the table
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8. Entering Field Names
 Field names:
 Short but descriptive
 Can contain alpha-numeric characters
 Can contain many symbols
 Can contain spaces
 Must start with a character or symbol
 May use naming convention
 Identify table, data type, and field description
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9. Identifying Data Types
 Data types identify the kind of data to be added to a
field
 Text
 Numbers
 Dates/Times
 Currency
 Setting a data type controls values that the field
contains
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10. AutoNumber Fields
 Fields that automatically number records as you add
them to a table
 Numbers can’t be entered or changed by user
 If you delete a record from a table, or cancel a new
row, Access never assigns the number to any new
record
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11. Field Properties
 Field Size determines how much data can be stored
 Some data type sizes are fixed – date/time, yes/no
 Format controls how a value is displayed
 Input Mask controls which keyboard entries will be
required and accepted
 Validation Rule sets limits on values that a field will
accept
 Validation Rule applies regardless of how data is entered
or changed
 Set Validation Text to explain how to correct an entry
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12. Operators
 Operators are used in validation, calculations and
queries
 Comparison Operators:
 Relational Operators (=, >, <, <>, >=, <=)
 Patterns (Like)
 Compare to a list (In)
 Logical operators define how to tie tests together
 And, Or, Not
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13. Using Wildcards
 Used in patterns instead of specific characters
 Primary wildcards used:
 * Represents any number of characters
 ? Represents an individual character
 Examples:
 *Graham* locates all records with graham within the
text
 Gra?am locates all records with gra at the beginning of
the field value and am at the end of the field value with
only one letter between
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14. Relational Databases
 Have more than one table where tables are related to
each other
 One to one
 One to many
 Many to many
 A combination of fields may be used for the table’s
primary key
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15. One to Many Relationships
 Each table contains data about a specific subject
(customers, loans)
 Each table on the ‘one’ side has a primary key
 Primary key of the “one” table is a foreign key in the
many table

16. Many to Many Relationships
 Two tables are related, but can have many records in
each table in common
 One student can attend many courses; one course can be
attended by many students
 Implement a many to many relationship by creating a
pair of one to many relationships with a third table
 Third table is often referred to as a “join” or “junction”
table
 Entries in the join table point to rows in the original
tables

17. Foreign Key
 A foreign key points to a record in another table
 Foreign key “looks like” the related primary key
 Same number of fields
 Data types for each field must match
 Field names don’t matter

18. Referential Integrity
 Makes sure that the records in related tables are
consistent
 Must have a customer in the customer table for an order
assigned to that customer
 Avoids “orphans”
 Cannot delete a record or change the primary key in
the one table when associated records are in the many
table, unless have cascade delete and cascade update
enabled

19. Editing Data
 Making new entries, changing existing entries, and
deleting rows are all affected by referential integrity
 A customer can be added at any time
 Must have a customer before a loan can be entered and
associated with a customer
 Referential integrity doesn’t require entry into a foreign key
 Can delete a loan at any time, but can only delete a
customer if they don’t have any loans (assuming no
cascade delete)

20. Cascading Changes
 When referential integrity is enforced can choose to
include Cascade Update and/or Cascade Delete
 Cascade update passes changes to the primary key of the
“one” table to the related rows in the “many” table
 Cascade delete removes rows from the “many” table
when a primary key (row) is deleted from the “one” table

21. Relationships Window
 Where relationships between tables are created and
defined
 Related fields must have the same data type
 Autonumber is related to number field with long integer
field size
 The one table has a 1 next to it; the many has a next
to it

22. Autolookup Queries
 Use queries to automatically look up data from related
tables
 Must contain the foreign key from the many table
 Can add, change or delete data in the source tables