MIS 134 - Database Tables
Database Concepts
• Simple databases store information in only
one table. These simple databases are often
called flat file databases, or just flat
databases.
• More complex database programs, such as
Access, store information in multiple related
tables, thereby creating what are referred to
as relational databases
Database Concepts
• Tables are one of the types of database objects
you work with in Access.
• Other types include forms, queries, reports,
macros, and modules.
• Of these object types, only tables are used to
store information.
• The others are used to enter, manage,
manipulate, analyze, retrieve, or display the
information stored in tables
– to make the information as accessible and therefore
as useful as possible
Database Concepts
• In its most basic form, a database is the electronic
equivalent of an organized list of information.
– Typically, this information has a common subject or
purpose, such as the list of employees
Database Concepts
• This list is arranged in a table of columns and rows
– Each column represents a field
• a specific type of information about an employee: last name, first
name, hire date, and so on
– Each row represents a record
• all the information about a specific employee
• Storing the information in a database, has the following
advantages:
– It takes up far less space
– It costs less to reproduce and distribute
– If the database is designed correctly, the information can be
retrieved in many ways
• The real power of a database isn’t in its ability to store
information; it is in your ability to quickly retrieve exactly
the information you want from the database
Intuitive Database Design
• Let us take a look at a simple invoice.
• By inspecting the individual data items on the invoice,
the following main subjects can be derived:
– Customer (who orders products)
– Products/Services (ordered by the customer)
– Company (which sells the products)
• The database design process transforms user-perceived
objects (like an invoice) into conceptual database
objects (like Customer, Products, Company tables) and
ultimately into physical database objects
Company Information
Customer Information
Financial Information
Services Ordered
Products Ordered
The Relational Model
• Relational model defines
– the way data can be represented => data structure
– the way data can be protected => data integrity
– the operations that can be performed on data => data manipulation
• A relation is defined as a table of columns (attributes) and rows
(tuples)
– The definition specifies what will be contained in each column of
the table, but it does not include data.
– When you include rows of data, you have an instance of a relation.
• However, a relation has some very specific characteristics that
distinguish it from other rectangular ways of looking at data
– flat file or a spreadsheet
The Relational Model
• Column Characteristics:
– A name that is unique within the table
– The values in a column are drawn from only one domain
– Columns are subject to domain constraints
• Besides the data type (such as integer or Date/Time, for example),
other domain rules may be created for particular columns
• Row Characteristics:
– Only one value at the intersection of a column and a row. A
relation does not allow multivalued attributes
– There are no duplicate rows in a relation (Uniqueness)
– Rows in a relation are unordered.
– A primary key is a column or combination of columns that
uniquely identifies each row
Create Database
Default Database Folder
Options => Object Designers =>
AutoIndex on Import/Create
Status bar
• Across the bottom of the program window,
this bar displays information about the current
database and provides access to certain
program functions.
• At the right end of the bar is the View
Shortcuts toolbar, which provides convenient
buttons for switching the view of the active
database object
CREATE
• Buttons representing commands related to creating
database objects are organized on the Create tab in six
groups: Templates, Tables, Queries, Forms, Reports,
and Macros & Code.
• Double-clicking the active tab hides the ribbon’s button
groups and provides more space for the current
database object
Database Tables
• Tables are the core database objects.
– Their purpose is to store information.
– The purpose of every other database object is to
interact in some manner with one or more tables.
• A database can contain thousands of tables,
and the number of records each table can
contain is limited more by the storage space
available
• Datasheet view displays the table’s data in columns
(fields) and rows (records). The first row contains column
headings (field names)