Quizes 1+2 Flashcards
In Microsoft Access when defining relationships, do NOT select Enforce Referential Integrity to ensure the data is accurate. True or false?
false
The _____ key is an attribute in one table whose values must either match the primary key in another table or be null.
Foreign
The ____ key of a table is the column or collection of columns that uniquely identifies a row in the table.
Primary
A good data model should have all of the following characteristics EXCEPT:
a) stable and flexible
b) redundant
c) reusable
d) accurate
b) redundant
Another word for entity when referring to database design is…?
Table
Highest level data model that defines what the system should include?
Conceptual Data Model
Data model that includes relationships and entities but is independent of the DBMS.
Logical Data Model
Data model that includes the DBMS and storage estimates for all files and data.
Physical Data Model
At college, a student takes many courses and courses contain many students. What type of relationship is this?
M:N
Use the following datatype in Microsoft Access to store a customer number that has format of three letters, a hyphen and then four
numbers (for example CSN-5730).
Short Text
DBMS stands for:
Database Management System
Who should be involved in data modelling?
a) owners/ sponsors
b) business analysts and specialists
c) data modeler, process modeller, program designer, physical database designer
d) end users
e) all of the above
e) all of the above
In Microsoft Access, you must select save after entering a new record into a table. True or False?
False
Microsoft Access determines the relationships between tables automatically. True or False
False
Mandatory participation from one entity to another means the minimum cardinality is zero. True or False?
False
The cardinality expresses the number of of records in a related table that one record can be associated with. True or False?
True
A Chen ERD uses the following shape between entities to describe the relationship:
Diamond
Many to many (M:N) relationships cannot be created in a relational DBMS. They must be resolved by
a) enforcing referential integrity
b) setting the participation as optional
c) creating a bridge/ composite entity between the two entities
e) deleting one of the entities from the database
c) creating a bridge/ composite entity between the two entities
The maximum cardinality value is not shown in a Crow’s Foot diagram. True or False?
True
Question 15
Valid relationship types include: zero to zero (0:0), one to one (1:1), one to many (1:M) and many to many (M:N). True or False?
False
Connected entities are called…
participants
____ describes relationship classification–1:1, 1:M, M:N
Connectivity
What Cardinality expresses?
It expresses the number of entity occurrences(records) associated with one occurrence of related entity
In what Relationship Participation an entity occurrence does not require a corresponding occurrence in related entity?
Optional Relationship Participation
In what Relationship Participation an Entity occurrence requires corresponding occurrence in related entity
Mandatory Relationship Participation
–If no optionality symbol is shown on ERD, it is mandatory
Cardinality is also known as ….
the degree of the association
What Types of Relationships is created with a single relationship from one record in a table to a single record in another table ?
1:1
What Types of Relationships is created by including the primary key of the “one” table as a foreign key in the “many” table?
(1:M)
What Types of Relationships is created with a new table whose primary key is the combination of the primary keys of the original tables or new field created to represent PK?
(M:N)
In Chen’s Notation, what does a rectangle represent?
Tables
In Chen’s Notation, what does a diamond represent?
Relationships
An employee may have many degrees and each degree may have been earned by many employees. Employees are assigned to one project at a time. Each project can have many employees assigned to it.
What are the entities?
EMPLOYEES, DEGREES, PROJ
An employee may have many degrees and each degree may have been earned by many employees. Employees are assigned to one project at a time. Each project can have many employees assigned to it.
What are possible attributes within each entity?
EMPLOYEES(EMPID, LAST, FIRST, SALARY, DEPT, STARTDATE, PROJID);
DEGREES(DEGREEID, INSTITUTION, LEVEL, DISCIPLINE, ABBREVIATION);
PROJECTS(PROJID, PROJNAME, STARTDATE)
What is Data Modeling?
It is the process of creating a model for the data to be stored in a database. Helps in the visual representation of the data
What Data Model is represented by
WHAT the system contains?
Conceptual
What Data Model is represented by
HOW to create (independent of DBMS)?
Logical
What Data Model is represented by
HOW it is created using DBMS?
Physical
What is a Primary Key?
Unique identifier that labels a certain record
OR
Given that data, you can find that row
What is a Foreign Key?
A column/ field in a table also found in another table;
Provides the link between the tables;
May seem like duplicate data but is required to establish the relationship
PK => FK
1:M
PK => PK
1:1
