1. Relational Queries
(query 12) Display vendor contact info (contact person and phone number) for inventory products (relationship query)
Query: Inventory Product Info

2. EMPLOYEES
Employee#*
Department
DEPARTMENTS
Department name*
Inventory
Product number*
PURCHASE ORDERS
Product number
Emp Number M 1 M
Relational Concepts
Employees of a department make orders for requested products
Not all tables are linked
Only related ones
Two tables can have multiple relationships
Table relationships/links can be
One-to-many
One department can have many employees
One-to-one
In Access, can’t be many-to-many

3. Steps for Designing a Database
Understand application
Determine the entities in your business
Determine what tables you need
What properties (fields) does each table have?
What is the key of each table?
How to link tables?

4. Using Multiple Tables Linked fields don’t need to have the same name
E.g. Department & Department name
But must contain data of same data type
Field must be key in at least one table
primary table vs. related table
Referential Integrity:
Every department in EMPLOYEES (related table) must exist in DEPARTMENTS (primary table)
The link is activated by a Join operation
Inner Join
Left Outer Join
Right Outer Join
Try Vendors and Inventory

7. Using Multiple Tables How to create relationships between tables?
Relationship window
Tools  Relationships
Add tables to window
Right Click  Show Table
Remove tables from window
Select Table
Right Click  Hide Table
Join tables
Click on the field of one table and drag it over to the corresponding field in the other table
A window appears that describes the relationship

8. Key Field
3 Types of Joins
1 to many
Used when a record of Departments (primary (1st) table) has its Join field changed  what would happen to corresponding fields in Employees (related (2nd) table) records?
If not clicked  no ref. integrity
If clicked  Every record in related
Table must have a matching record in primary table; two other boxes
 Cascade Update
 Cascade Delete

9. The 1 is for the primary table
Referential Integrity: We can’t have a record in the related table that has no matching record in the primary table
Cascade Update  If join field of some record in primary table is updated
then update corresponding field in related table records
E.g., “Design”  “Development” in Departments, then automatically all
“Design” in Employees become “Development”
Cascade Delete  If record of some join field in primary table is deleted
then delete corresponding records related table
E.g. if we delete the “Design” department from Departments, then automatically delete all Employees record in the “Design” Department

10. Types of Joins
Decide how we go about concatenating records from related tables into 1 table
3 options are given : Reason: not all records in primary table have matching records in related table
E.g. Department = { (‘CSCI’, SJU), (‘MGMT’, SJU) , (‘ACCT’, CSB)}
Student (name, Department) … 2 CSCI, 1 MGMT and 2 HIST
Inner Join (1): includes data only from records have matches records in both tables
Left Outer Join (2): includes all records from primary even those that have no matches in related
Right Outer Join (3): includes all records from related even those that have no matches in primary
in case referential integrity is not specified
NO JOIN!

11. Types of Joins (Query that JOINS Purchase Orders & Inventory)
Drop Join and show result
Inner Join: Inventory items with outstanding purchase orders
Left Outer Join: All inventory items will be included even those with no outstanding purchase orders
Right Outer Join: All items with outstanding purchases are included even those not in inventory
NO JOIN!