Podcast
Questions and Answers
In the relational data model, a relation is another name for a record.
In the relational data model, a relation is another name for a record.
False
A superkey uniquely identifies a record within a table.
A superkey uniquely identifies a record within a table.
True
Each cell in a table can contain multiple values.
Each cell in a table can contain multiple values.
False
Primary key is a candidate key selected to identify records uniquely within a table.
Primary key is a candidate key selected to identify records uniquely within a table.
Signup and view all the answers
Order of columns in a relation has significance according to the relational model.
Order of columns in a relation has significance according to the relational model.
Signup and view all the answers
A domain in the relational model refers to the set of allowable values for all attributes in a relation.
A domain in the relational model refers to the set of allowable values for all attributes in a relation.
Signup and view all the answers
In a relational database, a Foreign Key column must always match a Primary Key value in the same table.
In a relational database, a Foreign Key column must always match a Primary Key value in the same table.
Signup and view all the answers
Null represents the absence of a value, which is the same as zero or spaces in a database.
Null represents the absence of a value, which is the same as zero or spaces in a database.
Signup and view all the answers
Referential Integrity states that if a Foreign Key exists in a table, its value must match the Primary Key value of some record in another table.
Referential Integrity states that if a Foreign Key exists in a table, its value must match the Primary Key value of some record in another table.
Signup and view all the answers
SQL (Structured Query Language) is the only relational language standardized by ISO.
SQL (Structured Query Language) is the only relational language standardized by ISO.
Signup and view all the answers
Entity Integrity rule dictates that in a base table, every column of a Primary Key can be null.
Entity Integrity rule dictates that in a base table, every column of a Primary Key can be null.
Signup and view all the answers
Study Notes
Relational Model
- The relational data model describes the world as a collection of relations (or tables).
- A data model is an integrated collection of concepts for describing data, relationships between data, and constraints on the data.
Components of Data Model
- A structural part
- A manipulative part
- A set of integrity rules
RM Terminology
- Relation: a table with columns and rows
- Attribute: a named column of a relation
- Domain: a set of allowable values for one or more attributes
- Tuple: a record of a relation
- Alternative terminology: table, column, record; file, field, row; relation, attribute, tuple
Properties of Relations
- Each table has a distinct name
- Each cell of a table contains exactly one atomic (single) value
- Each column has a distinct name
- Values of a column are all from the same domain
- Each record is distinct; there are no duplicate records
- Order of columns has no significance
- Order of records has no significance, theoretically
Relational Keys
- Superkey: a column, or a set of columns, that uniquely identifies a record within a table
- Candidate Key: a minimal superkey for a relation
- Primary Key: a candidate key selected to identify records uniquely within a table
- Alternate Keys: candidate keys that are not selected to be primary key
- Foreign Key: a column, or set of columns, within one table that matches a candidate key of some (possibly same) table
Relational Integrity
- Null represents a value for a column that is currently unknown or not applicable for a record
- Null deals with incomplete or exceptional data and represents the absence of a value
- Null is not the same as zero or spaces, which are values
Relational Languages
- SQL (Structured Query Language): a standardized language by ISO
- QBE (Query-by-Example): an alternative graphical “point-and-click” way of querying a database
Relational Integrity Rules
- Entity Integrity: in a base table, no column of a primary key can be null
- Referential Integrity: if a foreign key exists in a table, either the foreign key value must match a candidate key value of some record in its home table
- Business Rules: rules that define or constrain some aspect of the business
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Description
This quiz covers the fundamental concepts of the relational data model, including relations, attributes, domains, tuples, and more. Test your knowledge on the terminology and components of the relational model.
