Chapter 12 File Processing and Data Management Concepts

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Chapter 12File Processing and Data Management
Concepts
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Presentation Outline

1. Terminology
2. Database Technology
3. The Architecture of a Database Management System
   (DBMS)
4. The Database Administrator

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I. Terminology

1. Field
2. Data Occurrences
3. Fixed vs. Variable Length Records
4. Record Key
5. Sort Keys

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A. Field

• A field is the smallest block of data that will
  be stored and retrieved in the information
  system. Other names for field include data item,
  attribute, or element.

Field 1
Field 2
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B. Data Occurrences

• A specific set of data values for a record in a
  file.

1
2
3
4
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The above table contains 5 occurrences of account
records for the general ledger account file.
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C. Fixed vs. Variable Length Records

• Fixed Length Records
• Both the number of fields and the length of each
  field are fixed.
• Strength Easier to manipulate records.
• Weakness Must accommodate maximum sizes.

• Variable Length Records
• Both the number of fields and the length of each
  field are variable. (See Fig. 15-1 on p. 603)
• Strength Less waste of memory when maximum sizes
  do not have to be accomodated.
• Weakness Record manipulation is more difficult.

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D. Record Key
1110
1500
2105
2110

• A record key is a field or combination of fields
  that uniquely identifies a particular record in a
  file.

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E. Sort Keys

• Primary sort key The first field used to sort
  the data occurrences in a record set.
• Secondary sort key A field used to determine
  relative position among a set of data occurrences
  in a record set.
• Tertiary sort key Additional fields beyond
  primary and secondary sort keys that are required
  to uniquely identify data occurrences in a record
  set.

Last Name First Name Age
Adams Tom 25
Jones Alisa 36
Jones Julie 19
Jones Julie 21
Young Sam 22
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II. Database Technology

• The Problem of Redundancy
• The Components of a Database

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A. The Problem of Redundancy
That is not what we show per our records.

• Redundancy occurs when different areas of an
  organization use the information system to store
  the same information in more than one place.
• Results in update anomaly.

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B. The Components of a Database Management System

1. Data Description Language (DDL)
2. Data Manipulation Language (DML)
3. Data Query Language (DQL)

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1. Data Description Language (DDL)

• Defines the logical structure of the database
  (known as the schema). Defines the following
• Name of data fields.
• Type of data (numeric, alphabetic, etc.)
• Number of positions (length of field).
• May also define subschema (i.e., individual user
  views)

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2. Data Manipulation Language (DML)
Pull a trial balance.

• The DML consists of the commands for updating,
  editing, manipulating, and extracting data.
• Structured query language (SQL) is a common DML
  in relational settings.

Structure Query Language (SQL)
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3. Data Query Language
Query by Example (QBE)

• A data query language is a user friendly language
  or interface that allows the user to request
  information by simply filling in blanks.
  Represents a special type of DML.

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III. The Architecture of a Database Management
System (DBMS)

1. The Database Architecture
2. The Conceptual Architecture and
   Entity-Relationship (ER) Diagrams
3. Logical Data Structures
4. The Physical Structure

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A. The Database Architecture
Database contents Uses of database
Desired reports Information to be viewed
Conceptual Level
Logical data structures Tree
Network
Relational
Logical Level
Access Methods Sequential Access
Indexed Files
Physical Level
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B. The Conceptual Architecture and
Entity-Relationship (ER) Diagrams

• Square boxes are used for entities (separate
  tables).
• Ellipses are used for attributes (table columns).
• Diamond shaped boxes depict relationships.

PART_NO
NAME
COST
PART
STORED AT
LOCATION
WHSE
ADDRESS
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C. Logical Data Structures

• Tree or Hierarchical Structure
• Network Structures
• Relational Structure
• Selection
• Projection
• Join

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1. Tree or Hierarchical Structure

• A parent record can have many children. However
  a child record can have only one parent.
• Can only model 11 (one-to-one) and 1
  (one-to-many) relationships.
• Commonly used with accounting data. Can only
  access data by going from a parent to child.

Balance Sheet
Assets
Liabilities
Equity
Current Assets
Current Liabilities
Revenues
Long-term Assets
Long-term Liabilities
Expenses
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2. Network Structure

• Eliminates the distinction of parent and child
  records. A parent can have many children and a
  child can have many parents.
• Can model 11 (one-to-one), 1 (one-to-many),
  and (many-to-many) relationships.
• Must know the physical structure of the data in
  order to access it.

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3. Relational Structure

• Relational databases organize and store data in
  two dimensional tables consisting of rows and
  columns.
• Relationships among tables are represented by
  common data values in different tables.
• Straight forward in terms of organizing and
  searching the data.
• Possesses ad hoc search capabilities.

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3a. Selection

• Produces a horizontal subset (includes entire
  row) of a relation which satisfies a boolean
  predicate.

Savings Table
Name Acct Balance
John 123 35.75
Bill 205 3.95
Mary 707 7.95
Joe 127 4.05
(Savings)
Balance lt 5.00
Name Acct Balance
Bill 205 3.95
Joe 127 4.05
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3b. Projection

• Constructs a vertical subset of a relation. The
  subset is obtained by selecting specified
  attributes and removing others.

Savings Table
Name Acct Balance
John 123 35.75
Bill 205 3.95
Mary 707 7.95
Joe 127 4.05
(Savings)
Balance lt 5.00
Name
Name
Bill
Joe
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3c. Join

• A join is used to combine 2 tables. The
  attribute used to join must be in both tables.

Table R
Table S
A B C
a1 b1 c1
a2 b2 c2
a2 b2 c3
a4 b2 c2
C D E
c2 d1 e1
c3 d2 e3
c2 d1 e2
A B C D E
a2 b2 c2 d1 e1
a2 b2 c2 d1 e2
a2 b2 c3 d2 e3
a4 b2 c2 d1 e1
a4 b2 c2 d1 e2
R X S
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D. The Physical Structure

1. Sequential Access
2. Indexed Files

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1. Sequential Access

• Records can only be accessed in a predefined
  sequence. For example, if there are 100 records
  in a file, one must access the first 99 records
  before accessing the last record.
• Generally useful for batch processing when nearly
  all records must be accessed.

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2. Indexed Files

• Any attribute can be extracted from the records
  in a primary file and used to build a new file
  whose purpose is to provide an index to the
  original file.
• First, the index is searched to find a specified
  value of an attribute such as an customer account
  number.
• Second, the disk addresses are used to directly
  retrieve the desired records
• See Fig. 12-13 on p. 427.

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IV. The Database Administrator
This is not quite what we need.

• The database administrator is a person who
  coordinates data management activities such as
  approving the physical contents and user views of
  the database.

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Summary

• Fields and keys
• Three Components of a DBMS
• Three Types of Database Architecture
• The Database Administrator