Database

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Database

• Jons Head

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What is a database

• a collection of information stored in a computer
  in a systematic way
• Normally data stored in tables with relationship
  between tables
• Schema
• Data

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Common Databases

• Microsoft Access
• Microsoft SQL Server
• MySQL
• Oracle
• DB2

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What makes databases better than files

• Advanced Search
• Data Consistency
• Transactions
• Concurrent Use

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ACID

• Atomicity
• All activities in a transaction are performed or
  none of them are
• Consistency
• Data is consistent, so if row in one table points
  to a row in another table, that row will exist
• Isolation
• Appears that you are the only person using the
  database
• Durability
• Once data is committed it will remain through
  power off or other crashes

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Keys

• Simply a way to identify a row in a table
• Primary Key
• A unique id for every row in a table
• Foreign Key
• A unique way for a row in one table to point to a
  row in another table

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Index

• Instead of searching the hole table to find a row
  create an index to quickly jump to it
• B trees

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4
10
1
5
8
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Querying a database (Search)

• SQL Structured Query Language
• Select ______
• From _______
• Where ______