The Worlds of Database Systems

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The Worlds of Database Systems

• From Ch. 1 of A First Course in Database
  Systems, by J. D. Pullman and H. Widom

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Background

• Business applications of DBs
• maintaining internal records,
• presenting data to customers and clients on the
  WWW, and
• supporting many other commercial processes
• Scientific applications, representing data
  gathered
• by astronomers,
• by investigators of the human genome, and
• by biochemists exploring the medicinal properties
  of proteins,
• etc.

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Background

• A database management system (DBMS or a database
  system) is a powerful tool for creating and
  managing large amount of data efficiently and
  allowing it to persist over long period of time,
  safely.
• Capabilities of a DBMS
• Persistent storage
• Programming interface
• Transaction management

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1.1 The Evolution of Database Systems

• The DBMS is expected to
• Allow users to create new data and specify their
  schema.
• Give users the ability to query the data
• Support the storage of very large amount of data
• Control access to data from many users at once

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1.1.1 Early Database Management Systems

• The first commercial DBMS appears in late 1960s.
• Evolved from file systems
• Providing (3), storage of large amount of data
• No direct support of query language
• Supporting (1), a limited schema for the creation
  of directory structures of files
• Not satisfying (4)
• Applications of the first DBMS
• Airline reservation systems
• Banking systems
• Corporate Records

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1.1.2 Relational Database Systems
SELECT balance FROM Accounts WHERE accountNo67890
SELECT accountNo FROM Accounts WHERE
typesavings AND balance lt0
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1.1.3 Smaller and Smaller Systems

• Originally large and expensive
• Today
• many gigabytes fit on a single disk
• feasible to run a DBMS on a PC
• become available for even very small machines
• a common tool for computer applications, much as
  spreadsheet and word processors did before

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1.1.4 Bigger and Bigger Systems

• Corporate databases often occupy hundreds of
  gigabytes.
• Retails chains often store tetrabytes (1012
  bytes) of information recording the history of
  every sales made over a long period of time.
• Multimedia data
• An hour of video consumes about a gigabyte.
• Databases storing images from satellites can
  involve petabytes (1015 bytes) of data.
• Trends allowing DBSs to deal with large amount of
  data
• Tertiary storage
• Parallel computing

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1.1.5 Client-Server and Multi-Tier Architectures

• The simplest client/server architecture
• the entire DBMS is a server
• the query interfaces that interact with the user
  and send queries or other commands across to the
  server
• A trend to put more works in the client
• two tier (client/server) becoming three (or more)
  tiers
• The DBMS continues to acts as a server, but its
  client is typically an application server, which
  manages
• connection to the DBS, transaction,
  authorization, and other aspects

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1.1.6 Multimedia Data

• Common forms of multimedia data
• video, audio, radar signals, satellite images,
  and documents or pictures in various encoding
• The storage of multimedia data has forced DBMSs
  to expand in several ways.
• E.g., the operations that one performs on
  multimedia data are not the simple ones suitable
  for traditional data forms.
• To allow users to create and use complex data
  operations, DBMSs have to incorporate the
  ability of users to introduce functions of their
  own choosing.
• The size of multimedia objects also forces the
  DBMS to modify the storage manager so that
  objects or tuples of a gigabyte or more can be
  accommodated.

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1.1.7 Information Integration

• A large company has many divisions.
• Each has its own database of products
  independently of other divisions.
• These divisions may use different DBMSs,
  different structures for information, perhaps
  even different terms to mean the same thing or
  the same term to mean different things.
• Central control is not always the answer.
• One popular approach is the creation of data
  warehouses, where information from many legacy
  databases is copied, with the appropriate
  translation, to a central database

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1.2 Overview of a DBMS

• 1.2.1 Data-definition language commands
• 1.2.2 Overview of Query processing
• Answering the query
• Transaction processing
• 1.2.3 Storage and buffer management
• 1.2.4 Transaction Processing
• 1.2.5 The query processor

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Database management system components
Single boxes system components Double boxes
in-memory data structures Solid lines control
and data flow Dashed lines data flow only
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1.3 Outline of Database-System Studies

• Design of databases
• Chapters 2, 3 and 4
• Database programming
• Chapters 5 through 10
• Database system implementation
• Storage management
• Query processing
• Transaction management