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Relational Databases

QuestionAnswer
What are the three models of database system that have dominated over the history of database management systems? a. hierarchical Model b.relational model c.network models
What is the relational term for a row of related data values? tuple
How are the table name and the column names used in database study? row attribute
What is the relational term for a column in a row of records? attribute
What is the relational term for a collection of records about some object? relation name
How is the primary key denoted in a relation diagram? underlined
What is the term for a set of values each of the same data type in which each value is indivisible? domain
What term is used to refer to a value that is indivisible? atomic
What is the term that refers to the structure of a value? data type
What is the term for the description of a relation? schema
What is the relational term for a role or characteristic of a data element in a tuple of a relation?
Using common database notation, denote a relation, Part, that has attributes partno, name, cost and qoh. Part(part no,name,cost,qoh)
What is the term that refers to the number of attributes in a relation schema? degree
What is the term that refers to a relation and all of its tuples at an instant in time? Relation State
Does a relation in relational database theory have an order? False
A domain, months, has a possible range of 12 values, January, February, March, etc. What is the term for the number of values in a domain? cardinality
What is the term for the state of a relation that meets all constraints as defined in the relation schema? Valid State
In a database attribute, a value that is unknown, exists but is not available, or is a value that is undefined is said to be __________. null
If a relation, CUSTOMER, and a relation, VENDOR, both have a primary key, id, how would a user reference the two with dot notation in a query that uses both? customer.id vendor.id
What is the term that refers to restrictions on the actual values in a database state? Constraints
What kind of constraint can be expressed in a schema of a data model? explicit
What kind of constraint is just part of the relational data model? implicit
What is the term for constraints that cannot be directly expressed in schemas and must be expressed and enforced by an application program? Business Rules
List five of the domain constraints that we studied a. Booleans b. Characters c. time d. money e. fixed length strings
What is the term for any combination of attributes that can be uniquely used to identify a database record? Superkey
What is the term for a superkey from which one cannot remove any attributes and still have the uniqueness constraint? Key
A relation can have more than one key, so what is the term for another one of those keys? Candidate Key
What is the term for a candidate key that is used to identify a relation? primary key
What is the term for a candidate key that is NOT used to identify a relation? foreign key
What displaying the structure of a relation, how is the primary key identified? Underlined
What does the entity integrity constraint specify? No primary key can be null
What is the key constraint? Uniqueness
What is the term for a constraint that is specified between two relations in order to maintain consistency between the two relations? referential integrity constraint
What are the two requirement specified for a foreign key? a.Attributes in foreign key have same domain as primary key attributes Not yet graded b. Value of foreign key in a tuple of the current state either occur as a value of primary key or be null
What do you call constraints that may be specified by application programs or some general purpose constraint definition language rather than the data definition language? semantic integrity constraints
What constraint states that the value of one attribute determines the value of a different attribute? functional dependency constraint
What are the three operations that change the state of a relation? a. insert b. delete c. update
How could an INSERT operation on a relation cause a violation of the key constraint? if a key value in the new tuple already exists in another tuple relation.
How could an INSERT operation on a relation cause a violation of the entity integrity constraint? if any part of the primary key of a new tuple is null
How could an INSERT operation on a relation cause a violation of the referential integrity constraint? if value of foreign key in the new tuple refers to a tuple that doe not exist in the referenced relation.
What is the default action caused by a violation of any constraint of the relational database? reject
How could a DELETE operation on a relation cause a violation of the key constraint? does not violate key constraint
How could a DELETE operation on a relation cause a violation of the entity integrity constraint? does not violate entity integrity
An alternative to rejecting a DELETE operation that removes a tuple with a primary key that is being referenced by another tuple’s foreign key is to CASCADE. What occurs with a CASCADE action? delete all referring tuples
What is another alternative to REJECT and CASCADE, when a DELETE operation removes a tuple with a primary key that is being referenced by another tuple’s foreign key? set to null
What is the term for an executing program that includes one or more database operations? transaction