DB 3

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  1. Requirements to be a relation (6)
    • Every relation has a unique name
    • Every attribute value is atomic
    • Every row is unique
    • Attributes in a given table have unique names
    • The order of the columns is irrelevant
    • The order of the rows is irrelevant
  2. Normalization
    • A process for evaluating and correcting table tructures to minimze data redundancies, thereby reducing the likelihood of data anomalies
    • decomposing relations to produce smaller, well strucuted relations
    • "check" against potential mistakes that might be in the structure of the database tables
  3. What is considered a well structured relation
    • a relation that contains minimal data redundancy and allows users to insert, delete, and update rows without causing data inconsistencies
    • A table should not pertain to more than one entity type
  4. Any relation that does not have multi valued attributes
    First Normal Form, atomic, any valid relation is in 1NF by definition
  5. Normalization processes
    • Eliminate repeating groups (multivalued attributes)
    • Identify the primary key
    • Identify all dependencies
  6. Relation that every key attribute is fully functionally dependent on the primary key
    Second normal form, no partial functional dependencies
  7. Any relation in 1NF that has a single attribute primary key
    is already in 2NF
  8. A relation that contains no transitive dependencies
  9. Converting to 3NF
    • Make new tables to eliminate transitive dependencies
    • Reassign corresponding dependent attributes
  10. Converting to 2NF
    • Make new tables to eliminate partial dependencies
    • Reassign the corresponding dependent attributes
  11. BCNF
    Boyce-Codd Normal form, a table is in this form if every determinant in the table is a candidate key
  12. Criteria for a well designed database
    • No redundancy
    • No partial dependencies
    • No transitive dependencies
  13. How to create a good database design
    • Identify entities involved and their relevant attribute and identifiers
    • Define relationships between entities
    • Draw an ER / EER diagram to model the problem
    • Transform the ER / EER model to a reltional schema
    • Normalize the relations up to BCNF
Card Set:
DB 3
2016-09-21 18:03:52

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