Databases Ch 3

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Databases Ch 3
2012-09-05 14:48:33

Database Processing
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  1. Characteristics of Relations
    • Rows contain data about an entity
    • Columns contain data about attributes of the entities
    • 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
  2. Entity
    some identifiable thing
  3. Three sources for databases.
    • existing data
    • development of new information systems
    • redesign of existing databases
  4. Columns
  5. Rows
    Tuples (rhymes with "couples")
  6. File
    Table, Relation
  7. Field
    Column, Attribute
  8. Record
    Row, Tuple
  9. Functional Dependency
    the value of one or more attributes determines the value of another attribute
  10. Composite Determinant
    two or more attributes determine the value of another
  11. Determinant
    the attribute that determines the value of another attribute or set of attributes
  12. Candidate Key
    a determinant that determines all of the other columns in a relation
  13. Primary Key
    one of the candidate keys that is selected to as the primary means for finding rows in a table - one per table - can have one column or be composite
  14. Surrogate Key
    artificial column that is added to a table to serve as the primary key
  15. Foreign Key
    a column or composite of columns that is the pirmary key of a table other than the one in which it appears
  16. Referential Integrity Constraint
    a statement that limits the values of the foreign key (ensures that the values of a foreign key match a valid value of a primary key)
  17. Three types of anomalies:
    • Deletion anomaly
    • Insertion anomaly
    • Update anomaly
  18. A table that duplicates data is succeptible to anomalies and is said to have ________.
    Data Integrity Problems
  19. Deletion Anomaly
    when one row is deleted, then the structure of the table forces facts about multiple things to be lost
  20. Insertion Anomaly
    the structure of the table forces us to enter facts about two or more entities when we just want to enter facts about one
  21. Update Anomaly
    updating a table may create data inconsistency