LIS3784 A2

Ch3Q3: Briefly describe a candidate key:

A candidate key can be described as a superkey without unnecessary attributes, that is, a minimal superkey.

Ch4Q8: The Crow's foot symbol with two parallel lines indicates ____ cardinality.

(1:1)

Ch4Q2: In the ERD, cardinality is indicated using the ____ notation.

(min, max)

Ch3Q13: ____ relational type is the "relational model ideal."

1:M

Ch3Q1: Why are entity integrity and referential integrity important in a database?

Entity integrity ensures that each row is uniquely identified by the primary key. Referential integrity means that, if the foreign key contains a value, that value refers to an existing valid tuple (row) in another relation.

Ch3Q7: ____ yields only the rows that appear in both tables.

INTERSECT

Ch3Q4: Briefly explain why a data dictionary is necessary, and what should be included in a data dictionary."

The main benefits of using one are the database is simplified and information is easier to understand especially its tables and indexes.

Ch3Q5: A CUSTOMER table's primary key is CUS_CODE. The CUSTOMER primary key column has no null entries, and all entries are unique. This is an example of ____ integrity.

a. entity

Ch4Q10: A(n) ____ entity is composed of the primary keys of each of the entities to be connected.

associative

Ch3Q6: ____ combines all rows from two tables, excluding duplicate rows.

b. UNION

Ch3Q2: A ____ key is defined as a key that is used strictly for data retrieval purposes.

d. secondary

Ch3Q10: A ____ contains at least all of the attribute names and characteristics for each table in the system.

data dictionary

Ch4Q7: The existence of a(n) ____ relationship indicates that the minimum cardinality is at least 1 for the mandatory entity.

mandatory

Ch3Q8: A(n) ____ join links tables by selecting only the rows with common values in their common attribute(s).

natural

Ch3Q9: In an outer join, the matched pairs would be retained and any unmatched values in the other table would be left ____.

null

Ch4Q6: The term "____" is used to label any condition in which one or more optional relationships exist.

optionally

Ch4Q1: A ____ should be a derived attribute.

person's age

Ch3Q14: Since it is used to link the tables that originally were related in a M:N relationship, the composite entity structure includes—as foreign keys—at least the ____ keys of the tables that are to be linked.

primary

Ch4Q9: If an employee within an EMPLOYEE entity has a relationship with itself, that relationship is known as a ____ relationship.

recursive

Ch4Q3: Another word for existence-independent is ____.

strong

Ch3Q12: In a database context, a(n) ____ indicates the use of different names to describe the same attribute.

synonym

Ch3Q11: The ____ is actually a system-created database whose tables store the user/designer-created database characteristics and contents.

system catalog

Ch3Q15: When you define a table's primary key, the DBMS automatically creates a(n) ____ index on the primary key column(s) you declared.

unique

Ch4Q4: When the PK of one entity does not contain the PK of a related entity, the relationship is ____.

weak

Ch4Q5: A ____ entity has a primary key that is partially or totally derived from the parent entity in the relationship.

weak