1. Review: Application of Database Systems
ER-diagram
Tables and their relationships
Application of
Database Systems
Queries
Reports
Not covered in midterm

2. ER-diagram
Entity types
Strong entity type
Weak entity type
Relationships
Cardinality constraints: 1:1, 1:M, M:N - relationship
Participation constraints: mandatory, optional
Attributes
atomic attributes
composite attributes
single-valued, multi-valued attributes
derived attributes
key, partial key, surrogate key, non-key attribute

3. department employee project dependent works for controls manages
works on
dependents of
controls
supervision
bdate
ssn
name
lname
minit
fname
sex
address
salary
birthdate
relationship
number
location
number of
employees
startdate
hours 1 N
supervisor
supervisee M
degree

4. Mapping from ER-diagrams onto relational schemas
1. Create a relation for each strong entity type
2. Create a relation for each weak entity type
3. For each binary 1:1 relationship choose an entity and include the
other’s PK in it as an FK
4. For each binary 1:n relationship, choose the n-side entity and include
an FK with respect to the other entity.
5. For each binary M:N relationship, create a relation for the relationship
6. For each multi-valued attribute create a new relation
7. For each n-ary relationship, create a relation for the relationship

5. fname, minit, lname, ssn, bdate, address, sex, salary, superssn, dno
Dname, dnumber, mgrssn, mgrstartdate
Dnumber, dlocation
Pname, pnumber, plocation, dnum
Essn, pno, hours
Essn, dependentname, sex, bdate, relationship
EMPLOYEE
DEPARTMENT
DEPT _LOCATIONS
WORKS_ON
PROJECT
DEPENDENT

6. About participation constraints
If a relationship is mandatory for an entity set, then
if the entity set is on the “many” side of the relationship, then a specification is required to ensure a foreign key has a value, and that it cannot be null
setting the ‘required’ property for the FK in MS Access, or
NOT NULL constraint in the DDL. N A c d B x y 1

7. A B c d x y c
The “required” property for attribute c
is set “yes”.

8. Setting the required
property to Yes

9. If the entity set is on the “one” side of a relationship, then a check constraint or database trigger can be specified to ensure compliance. c d x y 1 N A B

10. A B c d x y c
A program should be produced to check that any value
appearing in c-column in table A must appear at least
once in c-column in table B.

11. Five different ways to create tables
Using Table Wizard
Using data sheet view
Using design view
Creating tables with queries
Creating tables by importing external data sources

12. Creating a Table in Design View
If you want to create the basic table structure yourself and define all the field names and data types, you can create the table in Design view.

14. Data Types of Fields
Attachment    Files, such as digital photos. Multiple files can be attached per record. This data type is not available in earlier versions of Access.
AutoNumber    Numbers that are automatically generated for each record.
Currency    Monetary values.
Date/Time    Dates and times.
Hyperlink    Hyperlinks, such as addresses.
Memo    Long blocks of text and text that use text formatting. A typical use of a Memo field would be a detailed product description.
Number    Numeric values, such as distances. Note that there is a separate data type for currency.
OLE Object    OLE objects (OLE object: An object supporting the OLE protocol for object linking and embedding.
Text    Short, alphanumeric values, such as a last name or a street address.
Yes/No    Boolean values.

15. Located in the lower pane of Table Design View
Field Size property
Caption property
Field Properties can be used to specify characteristics for individual fields
Located in the lower pane of Table Design View

16. Properties (1 of 2) Field size- Adjusts the size of the text field
Format- changes the way field is displayed. Does not effect the value.
Input Mask- facilitates data entry
Caption- Label used for the field
Default Value- the automatically entered value

17. Properties (2 of 2)
Validation Rule- Rejects records that do not conform to rules entered.
Validation Text- Error returned when validation rule is broken.
Required- Forces user to enter in value if selected.
Allow Zero Length- Allows text length of 0.
Indexed- increases efficiency of search on the field

18. Examples for Format property
Format property for Number data type:
#,###.##;(#,###.##)[Red];0,000.00;“Undefined”
format for positive
number
format for 0
format for null-value
format for negative
number
6,789.77

19. Examples for Input Mask property
Input mask forText data type:
!\(999") "000\-0000;0;_ - (204)
>!“FJ”\-AA\ – FJ-EA-12048
Input mask for Time data type
99:00:00\ >LL;0;_ - 05:56:00 PM

20. Create Tables – Consider a Foreign Key
Customer ID - Primary Key in Customer Table
Customer ID –will only appear in one record - there must only be one unique id per customer
Customer ID - Regular Field in Orders Table
Customer ID may appear many times – one customer can place many orders
Based on the above example:
Customer Id is the foreign key in the Orders table
This is referred to as a One to Many Relationship

21. Referential Integrity
(i) Consider two relation schemas R1 and R2;
The attributes in FK (foreign key) in R1 have the same domain(s) as the primary key attributes PK (primary key) in R2; the attributes FK are said to reference or refer to the relation R2.
iii) A value of FK in a tuple (record) t1 of the current state r(R1) either occurs as a value of PK for some tuple t2 in the current state r(R2) or is null. In the former case, we have t1[FK] = t2[PK], and we say that the tuple t1 references or refers to the tuple t2.
Example: FK
Order(OrderId, …, CustId)
Customer(CustId, … )

22. Working with Multiple Tables – Table Relationships
Relationship between two tables
The strength of Access is the fact that it is a relational database
This means you can have multiple tables and create relationships between each table
This helps eliminate redundant data

23. Working with Multiple Tables – Referential Integrity
Enforce Referential Integrity
Assures that the references to relationships between data is accurate
Established when creating the relationship between two tables

24. Working with Multiple tables - Cascades
Cascade update and cascade delete
When active, data changed in one table that is in a relationship will be changed in its related tables
Can be set when establishing relationships between tables

25. cascade – a strategy to enforce referential integrity
Employee
ssn
...
delete
Works-on
Essn
Pno 5
...
delete

26. cascade – a strategy to enforce referential integrity
Employee
delete
ssn
supervisor
null
Employee
ssn
supervisor
null
not reasonable
delete
delete

27. cascade – a strategy to enforce referential integrity
Employee
delete
ssn
supervisor
null
Employee
ssn
supervisor
null
reasonable
delete
delete

28. Creating a Table with a Query
A make table query retrieves data from one or more tables, and then loads the result set into a new table. That new table can reside in the database that you have open, or you can create it in another database.

29. Queries different kinds of queries: - select queries - action queries
Make-Table query
Delete query
Append-Table query
Update query
- Crosstab query
- total queries
Group by
Aggregate functions:
count, sum, maximum, minimum, average
- one-to-one relationship, one-to-many relationship

30. Using Query Design View
Tables pane
Design pane
Query Design grid has two panes – the table pane and the design pane
Striking the F6 key will toggle you between sections

31. Select Query
Searches associated tables and returns a dataset that matches the query parameters

32. Specifying Criteria – Currency and Operands
Currency amount entered without dollar sign
Greater than (>) operand
Specify criteria with currency
Without the dollar sign
With or without the decimal point
Use operands such as:
Less than and greater than
Equal to or not equal to

33. IS NULL finds only records that have no value
IS NOT NULL criteria and partial resulting dataset
Is Null criteria and resulting dataset
IS NULL finds only records that have no value
IS NOT NULL excludes Null value records

34. Specifying Criteria – And and Or
Or Criterion and resulting dataset
And criterion and resulting dataset
OR finds records that can match one or more conditions
AND finds records that must match all criteria specified

35. Database Analysis Tools
SELECT fname FROM customer
WHERE lname=“Smith”
ORDER BY fname
Returns records in the fname field only where the lname field is equal to Smith. Records are sorted in ascending order by first name
Clauses
- Added to statements to restrict/specify records
WHERE clause
- Specifies which records to return
ORDER BY clause
- Specifies sort order

36. Data Aggregates Use a Totals Query to Group
Grouping field
Field to be totaled
select Location, sum(Balance)
where Account, Branch
group by Location
Organizes query results into groups
Only use the field or fields that you want to total and the grouping field

37. Vid
Make
Model
Colour
Kilos
Year
Price
Sold 1
Toyota
Celica
Red
100000
1994
$15,000.00
Yes 2
Honda
Prelude
Blue
150000
$18,000.00 No 3
145000
1993
$15,500.00 4
1997
$22,000.00 5
1996 6 7 8
1995

38. Reports seven sections: - report header - page header - group header
- details
- group footer
- page footer
- report footer