1. Chapter 9 Database Systems
Introduction to CS
1st Semester, 2012 Sanghyun Park

2. Outline Database Fundamentals Data Models Relational Model
Object-Oriented Databases (skip)
Maintaining Database Integrity
Traditional File Structures
Data Mining (skip)
Social Impact of Database Technology (skip)

3. Database Fundamentals
A database is a collection of data that is ________, not necessarily physically, _________
A database management system (_______) defines, creates, and maintains a database
The DBMS also allows users _________ access to data in the database relying on schemas and subschemas
A ________ is a description of the entire database structure used by the DBMS
A __________ is a description of only that portion of the database ________ to a particular user’s needs
Databases have evolved as a means of _________ data storage systems

4. File vs. Database Organization (1/2)
___________ problem

5. File vs. Database Organization (2/2)

6. Layered Approach to Database Implementation
A typical database system consists of ____ layers – an _________ layer and a database management layer
Advantages of this dichotomy
Allows for the construction and use of _________ tools
Provides a means for controlling access to the databases
Achieves data _____________

7. Database Models A database model defines the _______ design of data
The model also describes the ____________ between different parts of data
In the history of database design, three models have been in use:
Hierarchical model
Network model
Relational model

8. Hierarchical Model Data are organized as a ____
Each entity has only ___ parent but can have several children

9. Network Model
Entities are organized in a _____, where some entities can be accessed through _______ paths
There is __ hierarchy

10. Relational Model (1/2)
Data are organized in two-dimensional ______ called _________
There is no hierarchical or network structure imposed on the data

11. Relational Model (2/2)
Each column in a relation is called an _________
The total number of attributes for a relation is called the ______ of the relation
Each row in a relation is called a _____
The total number of rows in a relation is called the __________ of the relation
The cardinality of a relation changes when tuples are added or deleted; this makes the database _________

12. Issues of Relational Design (1/4)
Lack of efficiency due to __________
Possibility of information ____ when deleting a tuple
The source of the problems is that we have combined more than one concept into a ______ relation

13. Issues of Relational Design (2/4)

14. Issues of Relational Design (3/4)
ASSIGNMENT relation
Job Id
Start Date
Term Date
S25X F5 S25Z * *
This database contains information about employees in EMPLOYEE relation, about available jobs in JOB relation, and about job history in ASSIGNMENT relation
Additional information is implicitly available by ________ the information from _________ relations

15. Issues of Relational Design (4/4)
Finding the department in which employee 23Y34 has worked

16. Relational Operations: SELECT

17. Relational Operations: PROJECT

18. Relational Operations: JOIN (1/3)

19. Relational Operations: JOIN (2/3)

20. Relational Operations: JOIN (3/3)

21. Issues of Implementation
The data in a database are actually stored in a ____ storage system
A DBMS allows the application software to be written in terms of a ______________
It is the duty of the ______ to accept commands in terms of the relational _____ and convert them into actions relative to the actual storage structure
The simplest way for a DBMS to implement a relation is to store it as a __________ file
To provide rapid access to entries, the DBMS would store the relation as an _______ file or utilize ________ techniques

22. Structured Query Language (1/2)
The language called ____ (Structured Query Language) is used extensively by application software programmers for manipulating databases
A query involving a combination of SELECT, PROJECT, and JOIN operations can be expressed as a _____ SQL statement
We should read a SQL statement as a description of the information ______ rather than a _________ of activities to be performed  not procedural but __________

23. Structured Query Language (2/2)
SELECT statement select EMPLOYEE.Name, ASSIGNMENT.StartDate from EMPLOYEE, ASSIGNMENT where EMPLOYEE.EmplId = ASSIGNMENT.EmplId
INSERT statement insert into EMPLOYEE values (‘42Z12’, ‘Sue A. Burt’, ‘33 Fair St.’, ‘ ’)
DELETE statement delete from EMPLOYEE where Name = ‘G. Jerry Smith’
UPDATE statement update EMPLOYEE set Address = ‘1812 Napoleon Ave.’ where Name = ‘Joe E. Baker’

24. Maintaining Database Integrity (1/2)
___________ is a sequence of operations that must all happen together (e.g., money transfer between accounts)
Before a transaction is allowed to alter the database, the alteration to be performed is first recorded in the ___
The point at which all the steps in a transaction have been recorded in the log is called the ____________
At this point DBMS becomes ________ to the transaction
If problems arise before a transaction has reached its commit point, the log can be used to _______ (undo) the activities actually performed by the transaction

25. Maintaining Database Integrity (2/2)
Simultaneous access problems
Incorrect summary problem
Lost update problem
______ is used for preventing others from accessing data being used by a transaction
Shared lock is used when ________ data
Exclusive lock is used when _________ data

26. Traditional File Structures
A ___ is an external collection of related data treated as a unit
The primary purpose of a file is to _____ data
Files are stored in what are known as ________ or _________ storage devices such as disk and tape
For our purposes, a file is a collection of data _______ with each record consisting of one or more _____
The _____ method determines how records can be retrieved: sequentially or randomly

27. Taxonomy of File Structures

28. Sequential Files While Not EOF {
Read the next record Process the record }

29. Applications of Sequential Files
The sequential file is used in applications that need to access ___ records from beginning to end
For example, if personal information about each employee is stored in a file, we can use sequential access to retrieve each record at the end of the month to print the paychecks
The sequential file is not efficient for _______ access

30. Indexed Files
To access a record in a file randomly, we need to know the _______ of the record
An indexed file is made of a data file, which is a sequential file, and an _____
The index itself is a very ____ file with only two fields: the ___ of the sequential file and the ________ of the corresponding record on the disk

31. Mapping in an Index File

32. Logical View of an Indexed File

33. Hashed Files
In an indexed file, the index _____ the key to the address; A hashed file uses a ________ to accomplish this mapping
The hashed file eliminates the need for an ____ file (index)
However, we will see that hashed files have their own problems

34. Modulo Division Hashing Method

35. Collision (1/2)
The population of keys is greater than the ______ of records in the data file
Because there are many keys for each address in the file, there is a possibility that more than one key will hash to the _____ address in the file
We call the set of keys that hash to the same address ________
A _______ is the event that occurs when a hashing algorithm produces an address for an insertion key, and that address is already occupied

36. Collision (2/2)

37. Collision Resolution: Open Addressing

38. Collision Resolution: Linked List Resolution

39. Collision Resolution: Bucket Hashing