Ch.2-Part 3 (Keys) Flashcards
1
Q
One (or more) column(S) of a relation that is (are) used to identify a row.
A
Key
2
Q
- A data value is unique for each row
- Key will uniquely identify a row
A
Unique Key
3
Q
A key that contains 2 or more attributes
A
Composite Key
4
Q
-A candidate key chosen to be the main key for the relation
A
Primary Key
5
Q
- A candidate to become the primary key
- Unique key
A
Candidate Key
6
Q
- Unique, numeric value that is added to a relation to serve as the primary key
- No meaning to users
- Usually hidden on forms
- Often used in place of a composite primary key
A
Surrogate key
7
Q
- Preserves the relationships b/w tables
- A primary key from one table placed into another table
A
Foreign Key
8
Q
No data was entered
- Often Ambiguous
- Column value is unknown
A
Null Value
