Chapter 2 The Relational Model
Primary Key
A candidate key selected to be the main key of a relation. (p. 66)
Alternate Key
A candidate key which was not chosen to be the primary key, but is still present in a relation. (p. 67)
Surrogate Key
A column with a unique, DBMS-assigned identifier that has been added to a table to be the primary key. (p. 70)
Table
A database structure of rows and columns used to create cells that hold data values. Also known as a relation or file. (p. 63)
AUTO_INCREMENT
A function MySQL uses to automatically assign surrogate key numbers. (p. 70)
SEQUENCE
A function Oracle Database uses to to define automatically increasing sequences of numbers that can be used as surrogate key numbers. (p. 70)
Row
A group of columns in a table. Also known as a tuple or record. (p. 63)
Composite Key
A key of a relation that consists of two or more columns. (p. 66)
Unique Key
A key that identifies a unique row. (p. 66)
Nonunique Key
A key that potentially identifies more than one row. (p. 66)
Column
A logical group of bytes in a row of a relation or a table. Also known as a(n) field or attribute. (p. 63)
Null Value
A missing value in a cell of a relation. (p. 74)
Referential Integrity Constraint
A relationship constraint on foreign key values. Specifies that the value of a foreign key must be a proper subset of the values of the primary key to which it refers. (p. 72)
Relation
A two-dimensional table consisting of rows and columns. Also known as a table or file. (p. 63)
Candidate Key
An attribute or a group of attributes that identifies a unique row in a relation. Can be chosen as the primary key. (p. 66)
Foreign Key
An attribute that is a key of one or more relations other than the one in which it appears. (p. 70)
Field
Another term for column or attribute. (p. 65)
Attribute
Another term for column or field. (p. 65)
Tuple
Another term for row or record. (p. 65)
Record
Another term for row or tuple. (p. 65)
File
Another term for table or relation. (p. 65)
Key
One or more columns of a relation that is used to identify a row. (p. 66)
Identity
Set of specifications that have been set to indicate to SQL Server that a surrogate key column exists. (p. 70)
Is Identity
Sets the value of a key to a surrogate.
Entity
Something of importance to the user that needs to be represented in the database. (p. 63)
Identity Increment
The amount that is added to each key value to create the next key. (p. 70)
Identity Seed
The starting value of a surrogate key. (p. 70)