Database Concepts Test 2
Dr Edgar F. Codd, after his extensive research on the Relational Model of database systems, came up with rules a database must obey in order to be regarded as a true relational database. How many are there?
12
Comprehensive Data Sub-Language Rule
A database can only be accessed using a language having linear syntax that supports data definition, data manipulation, and transaction management operations
Integrity Independence
A database must be independent of the application that uses it
High-Level Insert, Update, and Delete Rule
A database must support insertion, updation, and deletion by row, union, intersection, and minus operations
How is a relation instance defined?
A finite set of tuples in the relational database system
How is a relation schema defined?
A relation schema describes the relation name (table name), attributes, and their names
In a relational data model what is a tuple?
A single row
Regarding the mapping process of hierarchical entities, which of the following are included? Select all that apply.
Add primary keys of higher-level entities in the table of lower-level entities Create tables for all higher-level entities Declare primary key of higher-level table and the primary key for lower-level table
Which of the following are part of the Mapping Relationship process? Select all that apply.
Add the primary keys of all participating Entities as fields of table with their respective data types Declare a primary key composing all the primary keys of participating entities
View Updating Rule
All the views of a database, which can theoretically be updated, must also be updatable by the system
The SQL Data Definition Language uses which of the following set of commands to define database schema? Select all that apply.
Alter Create Drop
Which of the following are part of the Mapping Entity process? Select all that apply.
Create table for each entity Declare primary key
What do ER diagrams mainly comprise of? Select all that apply.
Entity attributes, Entities, Association among entities, and Relationships
Domain Constraints
Every attribute is bound to have a specific range of values
Guaranteed Access Rule
Every single data element is guaranteed to be accessible logically with a combination of table-name, primary key, and
Information Rule
Everything in a database must be stored in a table format
The WHERE clause does not define predicate or conditions, which must match in order to qualify the attributes to be projected.
False
Non-Subversion
If a system has an interface that provides access to low-level records, then the interface must not be able to subvert the records
The SQL Data Manipulation Language uses which of the following set of commands to modify the database instance? Select all that apply
Insert Update Delete
Candidate Keys
More than one such minimal subsets of attributes
Systematic Treatment of NULL Values
NULL values in a database must be given a systematic and uniform treatment
Physical Data Independence
The data stored in a database must be independent of the applications that access the database.
Distribution Independence
The end-user must not be able to see that the data is distributed across various locations
Logical Data Independence
The logical data stored in a database must be independent of its user's view
Active Online Catalog
The structure description of the entire database must be stored as a data dictionary
ER Model, when conceptualized into diagrams, gives a good overview of entity-relationship.
True
It is possible to create relational schema using ER diagram
True
SELECT is one of the fundamental query commands of SQL.
True
The FROM clause takes a relation name as an argument from which attributes are to be selected/projected.
True
We cannot import all the ER constraints into relational model, but an approximate schema can be generated.
True
Regarding inheritance, when the details of entities are generally hidden from the user, what is this known as?
abstraction
Insert Into/Values
for inserting values into the rows of tables (relation)
At UCF, everyone associated with the university is a Person. Each Person has a specific role they fulfill, Student, Faculty, Staff, and Maintenance. Based on the fact that the ER Model has the power of expressing database entities in a conceptual hierarchical manner, referencing Person, what would the entity be considered as?
generalization
The ER Model has the power of expressing database entities in a conceptual hierarchical manner. Going up in this structure is called what?
generalization
Referential integrity constraints
if a relation refers to a key attribute of a different or same relation, then that key element must exist
When using inheritance, which of the following is true?
lower-level entities to inherit the attributes of higher-level entities
Key
one minimal subset of attributes in the relation, which can identify a tuple uniquely
What is a relation key?
one or more attributes which can identify the tuple in the relation uniquely
What is the definition of a weak entity set?
one which does not have any primary key associated with it
Delete/From/
removing one or more rows from a table(relation)
What is the attribute domain?
some pre-defined value scope
At UCF, everyone associated with the university is a Person. Each Person has a specific role they fulfill, Student, Faculty, Staff, and Maintenance. Based on the fact that the ER Model has the power of expressing database entities in a conceptual hierarchical manner, referencing Student, what would the entity be considered as?
specialization
The ER Model has the power of expressing database entities in a conceptual hierarchical manner. Entities divided into sub-groups based on their characteristics is called what?
specialization
What is the format are relations saved in a relational data model?
tables
Update/Set/Where
updating or modifying the values of columns of tables(relation)