Database Course

Card Set Information

Database Course
2013-09-04 00:27:16

Cards for Database Designing
Show Answers:

  1. What is a column domain?
    Its range of permissible values. Eg. for gpa, the range is [0,4).
  2. What is a key?
    A key consists of one or more attributes that determine other attributes. For example, an invoice no. determines all the invoice attributes like invoice date and customer name.
  3. What is an entity?
    Person, place, thing, or event about which data will be collected and stored.
  4. What is an attribute?
    Characteristic of an entity.
  5. What is determination?
    Is the state in which knowing the value of one attribute makes it possible to determine the value of another.
  6. What is dependence?
    The value of one or more attributes is dependent upon the values of one or more other attributes. For example a student's last name may be determined by the student no.
  7. What is a superkey?
    It can uniquely identify any row in the table or functionally determine every attribute in the row.
  8. What is entity integrity?
    Is the condition in which each row in the table has its own unique identity.
  9. How do you ensure entity integrity?
    • a) All the values in the primary key must be unique.
    • b)No key attribute in the primary key can contain a null.
  10. What is a foreign key?
    The primary key of one table that has been placed into another table to create a common attribute.
  11. What is a secondary key?
    A key used strictly for data retrieval purposes.
  12. SELECT?
    Yields all values in rows in a table to satisfy a given condition.
  13. PROJECT?
    Yields all values for selected attributes or columns.
  14. UNION?
    Combines all rows from two tables, excluding duplicate rows.
    Yields only rows that appear in both tables.
    Yields all rows in one table that are not found in the other table.
  17. PRODUCT?
    Yields all possible pairs of rows from two tables.
  18. JOIN?
    Allows information to be combined from two or more tables. It allows the use of independent tables linked by common attributes.