Module 03a - Dependencies

Question 1

Define Entity

Answer 1

Some identifiable thing that users want to track

Question 2

Define Relation

Answer 2

Is a two-dimensional table that has the following characteristics:
Rows contain data about an entity.
Columns contain data about attributes of the entity.
All entries in a column are of the same kind.
Each column has a unique name.
Cells of the table hold a single value.
The order of the columns is unimportant.
The order of the rows is unimportant.
No two rows may be identical.

Question 3

Define Functional Dependency

Answer 3

When the value of one (set of) attribute(s) determines the value of a second (set of) attribute(s)

Question 4

Define Determinant

Answer 4

Attribute on the left side of the functional dependency

Question 5

Define Candidate Key

Answer 5

Is a key that determines all of the other columns in a relation.
If a relation has several candidate keys, one is chosen to be the primary key

Question 6

Define Composite Key

Answer 6

Is a key that consists of two or more columns

Question 7

Define Primary Key

Answer 7

Is a candidate key selected as the primary means of identifying rows in a relation

Question 8

Define Surrogate Key

Answer 8

Is an artificial column added to a relation to serve as a primary key

Question 9

Define Foreign Key

Answer 9

Is the primary key of one relation that is placed in another relation to form a link between the relations

Question 10

3 Constraints

Answer 10

Domain integrity constraint
Entity integrity constraint
Referential integrity constraint
The purpose of these three constraints, taken as a whole, is to create database integrity, which means that the data in our database will be useful, meaningful data.

Question 11

Define Normal Form

Answer 11

Database normalization (or normalisation) is the process of organizing the columns (attributes) and tables (relations) of a relational database to minimize data redundancy.

Question 12

Define multivalued dependency

Answer 12

In database theory, a multivalued dependency is a full constraint between two sets of attributes in a relation.

In contrast to the functional dependency, the multivalued dependency requires that certain tuples be present in a relation. Therefore, a multivalued dependency is a special case of tuple-generating dependency

Question 13

Alternative Terminology

Answer 13

Table - Column - Row
Relation - Tribute - Tuple
File - Field - Record

Question 14

Rules of Functional Dependency

Answer 14

If A –> (B, C), then A –> and A –> C

If (A,B) –> C, then neither A nor B determines C by itself

Question 15

Domain Integrity Constraint

Answer 15

Requirement that all of the values in a column are of the same kind

Question 16

Entity Integrity Constraint

Answer 16

Requirement that, in order to function properly, the primary key must have unique data values for every row in the table.
It means that this column is NOT NULL, and does not allow a NULL value in any row

Question 17

Referential Integrity Constraint

Answer 17

Statement that limits the values of the foreign key to those already existing as primary key values in the corresponding relation.