Access Lecture 1

Database Overview and Creating Tables

Create an Employee Table

Why database for 110A

• Because businesses generate a lot of data• What are some ways in which businesses

use data they collect?• Data is needed to generate meaningful

information• The bottom layer of a three tiered app• You’ll be more prepared for BUS111• So it is important to have working

knowledge of databases.

Overview of Access

What is a database and how is it different from database management system?– A collection of related tables.– MySJSU is a database which has tables all

related to you. Your profile, your classes and schedule, and your grades.

– Database Management System (DBMS) provides the means to store, maintain and gain access to the data.

Components of a Database

• Bits: 1 and 0• Bytes: 8 bits (11001100)• Field (aka column, attribute): Several Characters

(e.g. Name)• Record (aka row): Several Fields (e.g. your

school record)• Primary key: Unique identifier for the record (e.g.

SSN)• Table: Group of records e.g. (my class record). • Database: Group of related tables

An example of data stored in a database table

Different DBMS available in market?

• Oracle, DB2, Microsoft Access, Microsoft SQL Server, Firebird, PostgreSQL, MySQL, SQLite, FileMaker and Sybase Adaptive Server Enterprise (From Wikipedia – Click on link to read more)

• For this class we focus on MS Access (2007) and Microsoft SQL Server (express 2005 version)

Let’s look at one…

• This is a student database…Called Our_students_in_class_exercise

Steps in creating database

• Plan: Purpose of the database, its scope. Remember adding a bathroom after a house is build costs 10 times as much.

• Design: Build conceptual data models, report formats, data dictionary.

• Develop: Create tables, queries, reports• Implement: Populate the database and test• Review: Periodic checks to ensure compliance

Access Database Limitations

• 2 gigabytes in size

• Maximum of 32,768 objects

• 64 character maximum in an object name

• 14 character maximum for passwords

• Support up to 255 concurrent users

Access Table Limitations

• have up to 64 characters in each field name

• have up to 255 fields

• be one of 2048 concurrent open tables

• be up to 1 gigabyte

• have 32 indexes

• be sorted by up to 255 characters in one or more fields

Creating your own databases

• Say you are hired by a company to automate their employee payroll system.

• What are some of the fields that you can think of?

Creating your own databases

• Some potential fields– EmployeeID,– Hire Date– first name– last name– address phone number– birth date– Picture– pay scale– Hours worked

• You can get this information by analyzing the existing records of the company.

Creating your own database

• You may need several tables to create this database. Why?

• Creating several tables ensures easier access, faster processing, and removes redundancy

• You can join these tables with relationships using primary and foreign keys

Creating your own employee database

• New database blank database select location where file needs to be saved.

• Name the database as employee.• Create a new table using design view.

Explore other views for enhanced learning.• Notice different types of data types and

associated properties. • The first field is employeeID. Right click to

make it primary key.

Creating a table

• Add the remaining fields– Hire date : Date/time– Last/FirstName: Text– Street/City/State/Zip: Text (e.g. State 2chars)– Phone: Text– Birth Date: Text– Save the table as EmpMain

Populating Tables

• This means to add records• You don’t need to save as access automatically

updates the table. You can delete, modify, add records now.

• You can delete, modify, and add fields too.• However before you do this, you have to take

into account the data integrity issues.• You can play around with format, custom

properties, and other options to enhance the experience.

Let’s add some records

• Add 3 records, completing the following fields:– EmployeeID– HireDate– LastName– FirstName– Street/City/State/Zip– Phone– BirthDate

Relationships

• PRIMARY KEY: It is a field (or combination of fields) that makes each record in a table unique. Every table must have a primary key and each record must have a unique value as its primary key

• Tables and their relationships to each other are stored

• Tables are related in a one-to-many (or one-to-one) relationship

• A foreign key is required to establish the relationship – one table’s foreign key is another table’s primary key.

Primary Keys• PRIMARY KEY: It is a field (or combination of fields) that makes each record in a table

unique. Every table must have a primary key and each record must have a unique value as its primary key.

Primary keys

Examples of Properties

Properties of the CustomerID Field

Properties of the Gender Field

Data TypesDATA TYPE: Determines the type of data that can be entered and

the operations that can be performed on that data

Access recognizes the following data types:

• Number (can be used in calculations)

• Text (alphanumeric characters up to 255 per field)

• Memo (alphanumeric value of unlimited length)

• Date/Time • AutoNumber (numeric value,

automatically increases) • Yes/No • OLE Object • Currency Hyperlink

Data Type

Importing Data

• For your course project you’ll be importing data for your student table into your database.

• First click on the “External Data” Tab in Access

• Select the Excel as the file type that you’ll be getting the data from

• This starts a wizard

Importing Data

• There are 3 options…create a new table with the imported data, add the imported data to an existing table (this requires that the imported and existing data are similar), or link a table. Will do the first

• Browse to where the import file is and open

• Click open and OK

Importing Data

• You should be a preview of the data, Click Next

• Select the checkbox that says “first row contains column headings” and Next

• Now you can see the column headings as your field names and you can modify each fields datatype if you need to and Next

• Select the key if you wish

Importing Data• Now name your table something helpful

and your done.

• You can now go into the table in access and modify its design – you’ll probably need to…