Databases Ch1.txt

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Databases Ch1.txt
2012-09-05 14:20:24

Databases Ch 1
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  1. What is the purpose of a database?
    to help people keep track of things
  2. What is the most commonly used type of database?
    relational database
  3. What is the difference in data and information?
    Data: recorded facts and figures

    • Information: knowledge derived from data
    •                   data presented in a meaningful context
    •                   data processed by summing, ordering, averaging, grouping, comparing or other similar operations.
  4. Primary Key
    • means of uniquiely identifying each row in a relation/table
    • only one per relation
    • may be a composite key
    • ideal primary key is short, numeric and never changes
  5. Surrogate Key
    a primary key containing numbers that are automatically generated and assigned in the database itself
  6. What is the difference between a form and a report?
    one is input and one is output
  7. Composite Key
    a key that consists of two or more columns
  8. Candidate Key
    a key that determines all other columns (attributes) in a relation
  9. Key
    a combination of one or more columns that is used to identify rows in a relation
  10. Functional Dependency
    occurs when the value of one (set of) attribute(s) determines the value of a second (set of) attribute(s)
  11. Composite determinant
    a determinant of a functional dependency that consists of more than one attribute
  12. Data
    recorded facts and numbers
  13. Information
    • knowledge derived from data
    • data presented in a meaningful context
    • data processed by summing, ordering, averaging, grouping, comparing, etc.
  14. Table
    • has rows and columns like a spreadsheet
    • breaks databases into related things
  15. Column
    stores a characteristic common to all rows
  16. Record
    a row containing (recording) data for a specific instance
  17. Instance
    an occurance of a thing
  18. Row
    contains data about a particular occurance or instance of a thing of interest
  19. Database
    • stores data and relationships
    • records data in such a way that we can produce information from the data
  20. What are the four typical components of a database system?

    What's the fifth?
    users, database application, database management system (DBMS), and the database

    Structured Query Language (SQL)
  21. SQL
    Structured Query Language - an internationally recognized standard language that is understood by all commercial DBMS products.
  22. DBMS
    Database management system - a computer program used to create, process, and administer the database.
  23. Database application
    a set of one or more computer programs that serves as an intermediary between the user and the DBMS
  24. Basic functions of Application Programs:
    • create and process forms
    • process user queries
    • create and process reports
    • execute application logic
    • control application
  25. Form
    tells the database what the user needs to communicate - entry or input
  26. Query
    where the database is asked a question and it returns an answer
  27. Result set
    the answer to a query in an unformatted display - generally columnar
  28. Report
    answer generated by a query but instead of coming out in a result set, it comes out in a formatted display - through a report generator
  29. Database
    a self-describing collection of integrated tables.  Tables are integrated because they store data about the relationships between the rows of data, self-describing because it stores a description of itself.
  30. Referential integrity constraints
    rules that are enforced by the DBMS
  31. Functions of a DBMS
    • create database
    • create tables
    • create supporting structures (e.g., indexes)
    • read database data
    • modify (insert, update, or delete) database data
    • maintain database structures
    • enforce rules
    • control concurrency
    • provide security
    • perform backup and recovery
  32. Concurrency
    the number of people hitting the database at the same time
  33. The biggest issue with enterprise DBMS is:
    concurrency - the number of people hitting the database at the same time (e.g. one user's work interfering with another user's work)
  34. Examples of DBMS products:
    • Microsoft Access - low end not for professionals
    • Oracle Database
    • MySQL
  35. Integrated tables
    tables that store both data and the relationships among the data
  36. Metadata
    data about data - tables contained within a database that describe the data within that database (table names, number of columns, primary keys, etc.)
  37. Database contents:
    • tables of user data
    • metadata
    • indexes
    • stored procedures
    • triggers
    • security data
    • backup/recovery data
  38. What are the three types of database design?
    • 1. From existing data
    • 2. New systems development
    • 3. Database redesign
  39. Entity
    • some identifiable thing that users want to track (e.g. customers, computers, sales, etc.)
    • provides the content that goes into the relation
  40. Relation
    the structure that will become the table in the database
  41. Rules about relations:
    • rows contain data about an entity
    • columns contain data about attributes of the entity
    • all entries in a column are of the same kind
    • each column has a unique name
    • cells of the table hold a single value
    • the order of the columns is unimportant
    • the order of the rows is unimportant
    • no two rows may be identical
  42. In order to have a referential integrity we have to have a minimum of __ tables.
    • two
    • 2 tables = 1 referential integrity constraint
    • 3 tables = 2 referential integrity constraints
    • 4 tables = 3 referential integrity constraints etc.
  43. A value cannot exist in a ________ key if it does not exist in the _______ key.
    A value cannot exist in a foreign key if it does not exist in the primary key.