Card Set Information

2011-10-17 11:55:27

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  1. Database
    a structure that can store information about multiple types of entities, the attributes of these entities, and the relationships among the entities
  2. entity
    a person, place, object, event, or idea for which you want to store and process data
  3. attribute
    a characteristic or property of an entity; also a field or a column
  4. relationship
    an association between entities
  5. DBMS(database management system)
    a program, or a collection of programs through which users interact with a database. lets you create forms and reports quickly and easily, as well as obtain answers to questions about the data stored in a database
  6. primary key
    a minimal collection of columns (attributes) in a table on which all columns are functionally dependent and that is chosen as the main direct-access vehicle to individual rows
  7. common field
    field linking two tables
  8. field
    a characteristic or property of an entity; also called an attribute or a column
  9. record
    a collection of related fields; can be though of as a row in a table
  10. lets you change structure of database without requiring you to change
    programs to access database (forms and reports interacting with
    data independence
  11. programmer needs to update programs to match the new database structure (may just avoid changing database all together)
    data dependence
  12. data redundancy
    duplication of data or storing of the same data in more than one place
  13. problems of data redundancy
    wastes space, takes up memory, takes up time, have to fix each occurence, inconsistencies
  14. steps to design database
    1) Analysis of requirements, 2) Design 3) Implementation (Logical and Physical Design)
  15. Can a table represent more than one entity?
    each entity has its own table
  16. data type
    an attribute that specifies the type of data that the object can hold
  17. data file
    replaces paper file, file used to store data
  18. When does a database have integrity?
    when the data follows all the rules (or meets all the integrity constraints)
  19. What is another term for a table?
  20. What is another term for rows?
  21. What is a weak entity?
    • depends on another entity for its existence
    • (cannot be created without proper parent, if parent is deleted, delete weak entity)
  22. What are the rules used to identify keys?
    • 1) Choose key that will not change value over life of each instance of an entity type
    • *Must have valid values
    • *structure cannot indicate classifications, locations, etc
  23. foreign key
    a column (attribute) or collection of columns in a table whose value is required either to match the value of a primary key in a table or to be null
  24. candidate key
    a minimal collection of columns (attributes) in a table on which all columns are functionally dependent but that has not necessarily been chosen as the primary key
  25. cardinality
    the number of items that must be included in a relationship
  26. normalization
    process used to identify the existence of potential problems, known as update anomalies in the design of a relational database
  27. update anomaly
    an update problem that can occur in a database as a result of a faulty design
  28. nonkey column
    an attribute (column) that is not part of the primary key
  29. functional dependency
    1 depends on the other -- B has only 1 value and is functionally dependent on A
  30. transitive dependency
    functional dependency between 2 nonkey attributes which are both dependent on a 3rd attribute
  31. anomaly
    problem or inconsistency
  32. Physical design
    actualy implementation of the database
  33. logical design
    conceptual abstract model using ERD and the normalization process
  34. A > B mean
    A functionally determines B, A is needed to determine B
  35. B > A
    B functionally determines A... B is needed to determine A
  36. Can a row be multivalued?
  37. ER modeling and normalization are part of which
    design phase?
  38. Does normalization cause number of tables to
    expand or decrease?
  39. Up to what normal form is adequate for most
    business design processes?
  40. What does data redundancy cause?
    update anomalies (update, inconsistent data, additions, deletions)
  41. Why is a table with a single attribute in its
    primary key automatically in 2nf?
    no repeating groups, no nonkey column depends on only a portion of the primary key
  42. Is the conceptual model dependent on
    yes, both.
  43. entity type
    collection of entities that share common properties or characteristics
  44. Do supertype and subtypes share common
    yes, common attributes or relationships
  45. ERD and Normalization are a part of which design?
  46. What is a recursive relationship?
    urnary relationship, degree of 1- relationship between instances of 1 entity type; 1:1, 1:M, M:N
  47. What does a minimum cardinality of 0 mean?
    optional participation
  48. Minimum cardinality of 1?
    mandatory participation
  49. How are M:N relationships dealt with?
    1 entity relates to many instances of another entity; must be separated into additional 1:M relations >> intersection relation (keys would be made up of parent keys
  50. What do ERDs show?
    logical representation of the data of an organization(entities), relationships among entities, attributes of entities
  51. 1:1
    a single entity instance of one entit type is related to a single entity instance of another type, primary key of one would be foreign key in the other; key of either table can be placed as a foreign key in the other table
  52. 1:M
    a signle instance of one entity related to many instances of another entity, Parent-child relationship
  53. Parent child relationship
    Parent is one side (Primary table) , child is the many side (related table), place parent key of parent table in child table
  54. supertype entity
    generic entity type subdivided into subtypes
  55. subtype entity
    subset of a supertype that shares common attributes or relationships distinct from other subsets
  56. composite entity
    an entity in the entity-relationship model used to implement a many-to-many relationship
  57. dependent entity
    an entity that requires a relationship to another entity for identification
  58. independent entity
    an entity that does not require a relationship to another entity for identification
  59. what is ERM used for?
    allows us to identify relationships between entities
  60. multivalued attribute
    an attribute can have more than one value for each entity instance (or repeating groups) removed during normalization process in logical design, become entities of their own