Transcript What we`ve learnt

What we’ve learnt
Doc 5.69
Doc 5.70 Section 1-3
A simple database
• Related objects
• Tables hold the data
• Forms, reports, queries to access the data
Database FADS
• Create FADS
• Create object in FADS, e.g Owners table,
Ownersphone query
• Don’t need to create a new database for
each new object
• Database FADS is container for objects
Wizards can help
• Tables for standard components e.g
customers
• You can customise the standard components
• Report wizard generates reports
• Form Wizard generates forms
About tables
• Tell you about things (entities)
• Entities have characteristics (attributes)
such as names, addresses, ages
• Attributes are represented by fields in the
table
• Fields have data type - e.g number, dates.
• Access 97 provides default types, sizes you can change them.
Keys
• Data in the table is held in records
• Each record must have a unique identifier Primary Key
• Relationships between tables are
represented by Foreign Keys
• e.g Cats table has a field Ownerid
• Ownerid is the primary key (unique
identifier) of the owner in the Owners
table.
Data Model Diagram
Cats
Owners
Bookings
Queries that join tables
• Need data about Owners and Cats
• Vacbooster is a query that joins data from
two tables
• Temporary data - called a dynaset
• Doesn’t change the data in the tables
Joining Tables
• Relationships allow you to combine data
about more than one thing.
• E.g Cats and Owners, Students and staff,
Suppliers and products.
• Owners/Cats relationship is Each Owner
can own one or more cats
• One to Many relationship
• Must include the unique identifier of the
one as foreign key in many