1. Review Applications of Database Systems
Theory
Applications of
Database Systems
Practice

2. ER-diagram
Relational databases:
Theory Part
Referential integrity
Relation normalization

3. ER-diagram
Entity types
Strong entity type
Weak entity type
Attributes
atomic attributes
composite attributes
single-valued attributes
multi-valued attributes
Relationships
Cardinality constraints
Participation constraints
Identifying relationship, recursive relationship

4. Mapping from ER-diagrams onto relational schemas
Create a relation for each strong entity type
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. 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
Employee(SSN, …, Dno)
Dept(Dno, … )

6. Relationships Window ConsultantID is primary key in Consultant table
Relationship line
ConsultantID is foreign
key in Clients table

7. You cannot delete a Consultant without first deleting related Clients
Delete Record button
Click + to display
related records
You cannot delete a Consultant without first deleting related Clients

8. 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

9. Updating and constraints
delete
Delete the WORK_ON tuple with Essn = ‘ ’ and pno = 10.
When deleting, the referential constraint will be checked.
- The following deletion is not acceptable:
Delete the EMPLOYEE tuple with ssn = ‘ ’
- reject, cascade, modify

10. Cascade deletion – a strategy to enforce referential integrity
Employee
ssn
...
delete
Works-on
Essn
Pno 5
...
delete

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

12. This violates the entity constraint. Works-on
Modify (cascade updating) – a strategy to enforce referential integrity
ssn
...
Employee
Essn
Pno 5
delete
null
This violates the entity constraint.
Works-on

13. Modify (cascade updating) – a strategy to enforce referential
integrity
Employee
ssn
...
delete
Department
Dno
... 5
chairman
Department
null
Dno
... 5
chairman
This does not violate the entity constraint.

14. Normalization
We discuss four normal forms: first, second, third, and Boyce-Codd normal forms
1NF, 2NF, 3NF, and BCNF
Normalization is a process that “improves” a database design by generating relations that are of higher normal forms.
The objective of normalization:
“to create relations where every dependency is on the key, the whole key, and nothing but the key”.

15. Functional Dependencies
We say an attribute, B, has a functional dependency on another attribute, A, if for any two records, which have
the same value for A, then the values for B in these two records must be the same. We illustrate this as:
A  B
Example: Suppose we keep track of employee addresses, and we only track one address for each employee . Suppose each employee is identified by their unique employee number. We say there is a functional dependency of address on employee number:
employee number  address

16. If EmpNum is the PK then the FDs: EmpNum  EmpEmail EmpNum  EmpFname
EmpLname
123
John
Doe
456
Peter
Smith
555
Alan
Lee
633
Peter
Doe
787
Alan
Lee
If EmpNum is the PK then the FDs:
EmpNum  Emp
EmpNum  EmpFname
EmpNum  EmpLname
must exist.

17. Transitive dependency
Consider attributes A, B, and C, and where
A  B and B  C.
Functional dependencies are transitive, which means that we also have the functional dependency
A  C
We say that C is transitively dependent on A through B.

18. EmpNum  DeptNum
EmpNum Emp DeptNum DeptNname
DeptNum  DeptName
EmpNum Emp DeptNum DeptNname
DeptName is transitively dependent on EmpNum via DeptNum
EmpNum  DeptName

19. A partial dependency exists when an attribute B is functionally dependent on an attribute A, and A is a component of a multipart candidate key.
InvNum
LineNum
Qty
InvDate
Candidate keys: {InvNum, LineNum}
InvDate is partially dependent on {InvNum, LineNum} as InvNum is a determinant of InvDate and InvNum is part of a candidate key

20. First Normal Form
We say a relation is in 1NF if all values stored in the relation are single-valued and atomic.
1NF places restrictions on the structure of relations. Values must be simple.

21. Boyce-Codd Normal Form BCNF is defined very simply:
a relation is in BCNF if it is in 1NF and if every determinant is a candidate key.
InvNum
LineNum
ProdNum
Qty
InvNum, LineNum
ProdNum
{InvNum, LineNum} and {InvNum, ProdNum} are the two candidate keys.
Qty
InvNum, ProdNum
LineNum

22. Second Normal Form
A relation is in 2NF if it is in 1NF, and every non-key attribute is fully dependent on each candidate key.
2NF (and 3NF) both involve the concepts of key and non-key attributes.
A key attribute is any attribute that is part of a key; any attribute that is not a key attribute, is a non-key attribute.
Relations that are not in BCNF have data redundancies
A relation in 2NF will not have any partial dependencies

23. Consider this InvLine table (in 1NF):
InvNum
LineNum
ProdNum
Qty
InvDate
InvNum, LineNum
ProdNum
There are two candidate keys.
Qty
InvNum, ProdNum
LineNum
Qty is the only non-key attribute, and it is dependent on InvNum
InvNum
InvDate
Since there is a determinant that is not a candidate key, InvLine is not BCNF
InvLine is not 2NF since there is a partial dependency of InvDate on InvNum
InvLine is only in 1NF

24. InvNum
LineNum
ProdNum
Qty
InvNum
InvDate
inv_no
line_no
prod_no
prod_desc
qty
EmployeeDept
ename
ssn
bdate
address
dnumber
dname

25. Third Normal Form
a relation is in 3NF if the relation is in 1NF and all determinants of non-key attributes are candidate keys
That is, for any functional dependency: X  Y, where Y is a non-key attribute (or a set of non-key attributes), X is a candidate key.
this definition of 3NF differs from BCNF only in the specification of non-key attributes - 3NF is weaker than BCNF. (BCNF requires all determinants to be candidate keys.)
A relation in 3NF will not have any transitive dependencies

26. EmpNum
EmpName
DeptNum
DeptName
We correct the situation by decomposing the original relation into two 3NF relations. Note the decomposition is lossless.

27. {student_no, course_no}  instr_no instr_no  course_no
Instructor teaches one course only.
Student takes a course and has one instructor.
In 3NF, but not in BCNF:
{student_no, course_no}  instr_no
instr_no  course_no
since we have instr_no  course-no, but instr_no is not a
Candidate key.

28. course_no
instr_no
student_no
BCNF
{student_no, instr_no}  student_no
{student_no, instr_no}  instr_no
instr_no  course_no

29. Tables
Forms
Reports
Practice Part
Queries
Macros
not covered
VBA modules

30. Tables
- table name
- attribute name
- attribute data type
- attribute properties
- Primary key
- Foreign key

32. 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 URL 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.

33. Properties 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
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

34. 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

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

36. Forms
different components:
- bound controls
- unbound controls
- calculated controls
- drop-down list box (combo box)
- check box
- option group
- command buttons

39. Subforms

40. Subforms are generated using Wizard

41. Subsubforms

42. Subforms are generated using Subform/Subreport button

43. Switchboard is a special form created using Switchboard
manager (not covered)

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

48. Queries
different kinds of queries:
- select queries
- action queries
Make-Table query, Delete-Table query
Append-Table query, Update query
parameter query, unmatched query, find-duplicates query
- Crosstab query
- total queries
Group by
Aggregate functions:
Count, sum, maximum, minimum, Average

49. Queries
- unmatched queries

51. Query design grid

52. SQL statement
Select FirstName, LastName
From Employees
Where Salary > 40000

53. Structured Query Language
SELECT Orders.CustomerID, Orders.EmployeeID, Orders.OrderDate, Orders.Freight
FROM Orders
WHERE (((Orders.OrderDate)>#3/25/2010#)) OR (((Orders.EmployeeID)<7));

54. Structured Query Language
SELECT Orders.CustomerID, Orders.EmployeeID, Orders.OrderDate, Orders.Freight, [Order Details].Quantity
FROM Orders INNER JOIN [Order Details] ON Orders.OrderID = [Order Details].OrderID
WHERE (((Orders.OrderDate)>#3/25/2010#) AND (([Order Details].Quantity)>7)) OR (((Orders.EmployeeID)<7));

55. Relationships
a many-to-many relationship is created by generating
two one-to-many relationships.

56. Macros

57. Macro groups

58. VBA modules

59. Private Sub cmdHistoryForm_Click()
'Display the form
DoCmd.OpenForm("Employee"), , , , acFormEdit
End Sub
Private Sub cmdEmployeeForm_Click()
DoCmd.OpenForm("History"), , , , acReadOnly
Private Sub cmdExit_Click()
'Exit the application
intResponse = MsgBox("Do you want to exit the Compensation" & _
"application?", vbYesNo + vbCritical, "Exit Application?")
If intResponse = vbYes Then
Application.Quit acQuitPrompt
End If

60. Private Sub cmdSummaryReport_Click()
'This procedure defines an SQL query as the record source
'for the "Retirement Summary" report; the SQL statement
'returns all records
'Assign the report name to the strObjectName variable
strObjectName = "Retirement Summary"
'Declare a variable to store the SQL statement, define the
'SQL string
strSQL = "SELECT Employee.LastName, Employee.FirstName, " & _
"Office.Region, Contribution.PayDate," & _
"Contribution.[401KEmployee], " & _
"Contribution.[401KMatch], Contribution.[401KTotal], " & _
"FROM (Office INNER JOIN Employee ON Office.[OfficeNumber] = " & _
"Employee.[OfficeLocation])" & _
"INNER JOIN Contribution ON Employee.[SSN] = Contribution.[SSN];"