2/20: Ch. 6 Data Management

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2/20 Ch. 6 Data Management

• What is data?
• How is it stored?
• Traditional management storage techniques
  problems
• DBMS

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What is data? The Data Hierarchy

• BIT binary digit (0,1 Y,n On,off)
• BYTE combination of BITS which represent a
  CHARACTER
• FIELD collection of BYTES which represent a
  DATUM or fact
• RECORD collection of FIELDS which reflect a
  TRANSACTION
• FILE A collection of similar RECORDS
• DATABASE an organizations electronic library of
  FILES

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How is data stored?

• ENTITY person, place, thing, event about which
  data must be kept
• ATTRIBUTE description of a particular ENTITY
• KEY FIELD field used to retrieve, update, or
  sort RECORD

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How is Data Stored? The Key Field

• Field in each record that uniquely identifies a
  record for
• Retrieval
• Updating
• Sorting

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How is data stored? File Organization

• Sequential
• Tape oriented
• One file follows another
• Follows physical sequence
• ISAM Indexed Sequential Access Method
• Index tracks key fields, where each record is
  stored.
• Speeds up access to records

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How is data stored? File Organization

• Direct (or Random)
• Disk oriented
• Can be accessed without regard to physical
  sequence
• Transform algorithm
• Translates the key field into the physical
  location on disk.

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So Whats the Problem? History

• Traditional management storage techniques
• Each application was created independently
• Each application had its own database created
• Applications cannot share data
• Duplicate data exists across the organization
• Inefficiency Independence reign supreme

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Whats the Problem?

• Data Redundancy
• Duplicate data exists across the organization
• Program-Data Dependence
• Each application had its own database created
• Lack of Flexibility Data-Sharing
• Too expensive to mine the data for undiscovered
  relationships or information
• Poor security
• Who knows how many places your SSN is stored?

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The Database

• Organizations electronic library
• Stores manages data in a convenient form

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Database Management System

• Software to create maintain data
• Enables business applications to extract data
• Independent of specific computer programs

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The 3 Key Components of a DBMS

• Data definition language
• Defines data elements in database
• Data manipulation language
• Manipulates data for applications
• SQL Structured Query Language
• Emerging standard data manipulation language for
  relational databases
• Data dictionary
• Formal definitions of all variables in database
  Controls variety of database contents

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So Whats the Big Deal?

• The DBMS separates the physical location and
  conceptual (or logical) location of data in the
  file system.
• You dont have to know where the data is to
  access or manipulate it.
• PHYSICAL VIEW where is data physically?
• Drive, disk, surface, track, sector, record
• Tape, block, record number (key)
• LOGICAL VIEW what data is needed by application?
• Succession of facts needed by application
• Name, type, length of field

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Next Time

• Guest speaker Jeff Till, programmer
• Using MS Excel
• Pick up database concepts again after Midterm
  Exam.