Chapter 3 1- 30
All relations are tables, but not all tables are relations.
True
A characteristic of a relation is that the rows of a relation may hold identical values.
false
A combination key is a group of attributes that uniquely identifies a row.
false
A relation can have only one candidate key.
false
A tuple is a group of one or more columns that uniquely identifies a row.
false
Given the functional dependency (A, B) → C, then it is true that A → C and B → C.
false
Given the functional dependency A → B, then it is necessarily true that B → A.
false
In the functional dependency shown as A → B, B is the determinant.
false
It is possible to have a relation that does not have a key.
false
The columns of a relation are sometimes called tuples.
false
The functional dependency noted as A → B means that the value of A can be determined from the value of B.
false
A relation is a table that has special restrictions on it.
False
A candidate key is one of a group of keys that may serve as the primary key in a relation.
true
A characteristic of a relation is that the cells of the relation hold a single value.
true
A determinant of a functional dependency may or may not be unique in a relation.
true
A functional dependency is a relationship between attributes such that if we know the value of one attribute, we can determine the value of the other attribute.
true
A key can be composed of a group of attributes taken together.
true
A key is a combination of one or more columns that is used to identify particular rows in a relation.
true
A primary key is a candidate key that has been selected to uniquely identify rows in a relation.
true
A relation is a table composed of columns and rows.
true
A row can be uniquely identified by a key.
true
A surrogate key is an artificial column that is added to a relation to be its primary key.
true
Attribute Y is functionally dependent on attribute X if the value of attribute X determines the value of Y.
true
Functional dependencies can involve groups of attributes.
true
Given the functional dependency (A, B) → C, the attributes (A, B) are referred to as a composite determinant.
true
Given the functional dependency A → (B, C), then it is true that A → B and A → C.
true
If by knowing the value of A we can find the value of B, then we would say that B is functionally dependent on A.
true
In functional dependencies, the attribute whose value is known or given is referred to as the determinant.
true
In relational terms as defined by E.F. Codd, a column is called an attribute.
true
In relational terms as defined by E.F. Codd, a row is called a tuple.
true