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Database literacy and modeling
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BSYS 2060 Lecture 2 – Data Literacy & Data Modeling
We live in an information age where data is king.
Data often most valuable asset of a companye.g. Aeroplan worth more than Air Canada
We live in a data mash-up world.
Where does data belong?
You control completely
You don’t control the data at all
Self-hostedWebsite containing all your data
convenientNot so easy...
Trend is towards you controlling your data
Diaspora
Many “fly by night” Web 2.0 apps
Who owns data?
Building a database for an organization?
What is the organization’s mission?
What is the project’s mission?
What data is required to make good decisions or for other reporting needs?
What data is currently being collected?
How is the data collected being used?
What data should be collected?
What are the main data entities?These will become your tables
What are the required fields and field data types?
What are the relationships between the tables?
Select your tools?e.g. MS Access, MS SQL, MySQL, OracleWhat is being used now if anything?
Be careful of the hammer!To a hammer, everything looks like a nail. If you only know MS Access, you may see always see MS Access as the solution even when it’s not. If you only know MS Excel, it seems like the perfect choice!
Source:http://www.flickr.com/photos/fixersphotos/3199566032/
Normalization
A brief introduction to the first three forms...
“Normalization”
• In the field of relational database design, normalization is a systematic way of ensuring that a database structure is suitable for general-purpose querying and free of certain undesirable characteristics—insertion, update, and deletion anomalies—that could lead to a loss of data integrity.
Codd, E.F. The Relational Model for Database Management: Version 2. Addison-Wesley (1990), p. 271
“...insertion, update, and deletion anomalies...”
Until a Course Code is assigned to this record, it can not be inserted in the table
“...insertion, update, and deletion anomalies...”
An edit made to one record may not be made to ALL records for the same employee
“...insertion, update, and deletion anomalies...”
If the Course Code is deleted the information for the Faculty Member will be lost.
Three Normal Forms
• 1NF– Eliminate repeating groups– No redundant data
• 2NF– Eliminate independent data– All fields depend on Primary Key
• 3NF– Eliminate dependency on non-key fields– Fields do not depend on each other
Un-Normalized Table (i.e. Excel)
First Normal Form (1NF)
0NF – “un-normalized”
1NF
Second Normal Form (2NF)
1NF
2NF
Third Normal Form (3NF)
2NF
3NF
COMPREHENSIVE
Access Tutorial 2
Building a Database and Defining Table Relationships
Objectives
• Learn the guidelines for designing databases and setting field properties
• View and modify field data types and formatting
• Create a table in Design view• Define fields and specify a table’s primary key• Modify the structure of a table
New Perspectives on Microsoft Office Access 2007 41
Objectives
• Import data from an Excel worksheet• Create a table by importing an existing
table structure• Delete, rename, and move fields• Add data to a table by importing a text
file• Define a relationship between two tables
New Perspectives on Microsoft Office Access 2007 42
Guidelines for Designing Databases
• Identify all the fields needed to produce the required information
• Organize each piece of data into its smallest useful part
• Group related fields into tables• Determine each table’s primary key• Include a common field in related tables• Avoid data redundancy• Determine the properties of each field
New Perspectives on Microsoft Office Access 2007 43
Guidelines for Setting Field Properties• You must name each
field, table, and other object
• Choose an appropriate data type
New Perspectives on Microsoft Office Access 2007 44
Guidelines for Setting Field Properties
• The Field Size property defines a field value’s maximum storage size for Text, Number, and AutoNumber fields only– Byte– Integer– Long Integer– Single– Double– Replication ID– Decimal
New Perspectives on Microsoft Office Access 2007 45
Viewing and Modifying Field Data Types and Formatting
New Perspectives on Microsoft Office Access 2007 46
Creating a Table in Design View
New Perspectives on Microsoft Office Access 2007 47
Defining a Field in Design View
• In the Field Name box, type the name for the field, and then press the Tab key
• Accept the default Text data type, or click the arrow and select a different data type for the field. Press the Tab key
• Enter an optional description for the field, if necessary
• Use the Field Properties pane to type or select other field properties, as appropriate
New Perspectives on Microsoft Office Access 2007 48
Defining a Field in Design View
New Perspectives on Microsoft Office Access 2007 49
Specifying the Primary Key in Design View
• In the Table window in Design view, click in the row for the field you’ve chosen to be the primary key. If the primary key will consist of two or more fields, click the row selector for the first field, press and hold down the Ctrl key, and then click the row selector for each additional primary key field
• In the Tools group on the Table Tools Design tab, click the Primary Key button
New Perspectives on Microsoft Office Access 2007 50
Specifying the Primary Key in Design View
New Perspectives on Microsoft Office Access 2007 51
Moving a Field
• To move a field, you use the mouse to drag it to a new location in the Table window in Design view
New Perspectives on Microsoft Office Access 2007 52
Adding a Field Between Two Existing Fields
• In the Table window in Design view, select the row for the field above which you want to add a new field
• In the Tools group on the Table Tools Design tab, click the Insert Rows button
• Define the new field by entering the field name, data type, optional description, and any property specifications
New Perspectives on Microsoft Office Access 2007 53
Adding a Field Between Two Existing Fields
New Perspectives on Microsoft Office Access 2007 54
Importing Data from an Excel Worksheet
• The import process allows you to copy the data from a source without having to open the source file
• Click External Data on the Ribbon• Click the Excel button in the Import group to
start the wizard
New Perspectives on Microsoft Office Access 2007 55
Importing Data from an Excel Worksheet
New Perspectives on Microsoft Office Access 2007 56
Importing Data from an Excel Worksheet
New Perspectives on Microsoft Office Access 2007 57
Importing Data from an Excel Worksheet
New Perspectives on Microsoft Office Access 2007 58
Creating a Table by Importingan Existing Table Structure
• Make sure the External Data tab is the active tab on the Ribbon
• In the Import group, click the Access button• Click the Browse button• Navigate to the file• Make sure the Import tables, queries, forms,
reports, macros, and modules into the current database option button is selected, and then click the OK button
• Click the Options buttonNew Perspectives on Microsoft Office
Access 2007 59
Creating a Table by Importingan Existing Table Structure
New Perspectives on Microsoft Office Access 2007 60
Deleting a Field from a Table Structure
• In Datasheet view, select the column heading for the field you want to delete
• In the Fields & Columns group on the Datasheet tab, click the Delete button
or• In Design view, click in the Field Name box for
the field you want to delete• In the Tools group on the Table Tools Design
tab, click the Delete Rows buttonNew Perspectives on Microsoft Office
Access 2007 61
Deleting a Field from a Table Structure
New Perspectives on Microsoft Office Access 2007 62
Adding Data to a Table by Importing a Text File
• Click the External Data tab on the Ribbon• In the Import group, click the Text File button• Click the Browse button• Navigate to the file• Click the Append a copy of the records to the
table option button• Select the table• Click the OK button
New Perspectives on Microsoft Office Access 2007 63
Adding Data to a Table by Importing a Text File
New Perspectives on Microsoft Office Access 2007 64
Defining Table Relationships
• One of the most powerful features of a relational database management system is its ability to define relationships between tables
• You use a common field to relate one table to another
New Perspectives on Microsoft Office Access 2007 65
Defining Table Relationships
New Perspectives on Microsoft Office Access 2007 66
Defining Table Relationships
• A one-to-many relationship exists between two tables when one record in the first table matches zero, one, or many records in the second table, and when one record in the second table matches at most one record in the first table– The Primary table is the “one” in a one-to-many
relationship– The Related table is the “many” table
New Perspectives on Microsoft Office Access 2007 67
Defining Table Relationships
• Referential integrity is a set of rules that Access enforces to maintain consistency between related tables when you update data in a database
• The Relationships window illustrates the relationships among a database’s tables
• Click the Database Tools tab on the Ribbon• In the Show/Hide group on the Database Tools
tab, click the Relationships buttonNew Perspectives on Microsoft Office
Access 2007 68
Defining Table Relationships
New Perspectives on Microsoft Office Access 2007 69
Defining Table Relationships
New Perspectives on Microsoft Office Access 2007 70
Defining Table Relationships
New Perspectives on Microsoft Office Access 2007 71
