Midterm Study Guide Flashcards
Which of the following is software used to create, maintain, and provide controlled access to databases?
Database management system (DBMS)
Data that describe the properties of other data are:
metadata.
A(n) ________ is often developed by identifying a form or report that a user needs on a regular basis.
user view
A person, place, object, event, or concept about which the organization wishes to maintain data is called a(n):
entity
The SDLC phase in which database processing programs are created is the ________ phase.
implementation
________ is a tool even non-programmers can use to access information from a database.
Structured query language
The traditional methodology used to develop, maintain, and replace information systems is called the:
Systems Development Life Cycle.
Legacy systems often contain data of ________ quality and are generally hosted on ________.
poor; mainframes
An iterative methodology that rapidly repeats the analysis, design, and implementation phases of the SDLC is called:
RAD - Rapid Application Development
Which organizational function should set database standards?
Database Administration
Metatdata typically describes all of the following EXCEPT:
location on disk
The SDLC phase in which every data attribute is defined, every category of data is listed, and every business relationship between data entities is defined is called the ________ phase.
design
________ are established between entities in a well-structured database so that the desired information can be retrieved.
Relationships
All of the following are primary purposes of a database management system (DBMS) EXCEPT:
providing an integrated development environment
A rule that CANNOT be violated by database users is called a:
constraint
An attribute that can be calculated from related attribute values is called a ________ attribute.
derived
In the figure below, which attribute is multivalued?
Employee_ID
Employee_Name
Address
Date_Employed
(Skill)
[Years_Employed]
Skill
Customers, cars, and parts are examples of:
Entities
Which of the following criteria should be considered when selecting an identifier?
Choose an identifier that doesn’t have large composite attributes
A(n) ________ is the relationship between a weak entity type and its owner.
identifying relationship
In the figure below, which attribute is derived?
Employee_ID
Employee_Name
Address
Date_Employed
(Skill)
[Years_Employed]
Years_Employed
Data modeling may be the most important part of the systems development process because:
data characteristics are important in the design of programs and other systems components
An entity type whose existence depends on another entity type is called a ________ entity.
weak
The following figure shows an example of:
[Employee]====<[[Dependent]]
a strong entity and its associated weak entity
Which of the following is NOT a characteristic of a good business rule?
Inconsistent
An attribute that must be present for every entity (or relationship) instance is a(n):
required attribute
An attribute that can be broken down into smaller parts is called a(n) ________ attribute.
composite
Which of the following is NOT a good characteristic of a data name?
Relates to a technical characteristic of the system
The most common types of entities are:
strong entities
Which of the following is an entity that exists independently of other entity types?
Strong
In the following diagram, which answer is true?
Each employee can supervise one employee, no employees, or many employees
A relationship where the minimum and maximum cardinality are both one is a(n) ________ relationship.
mandatory one
The number of entity types that participate in a Unary relationship is:
One
A simultaneous relationship among the instances of three entity types is called a ________ relationship.
Ternary
For the relationship represented in the figure below, which of the following is true?
[Employee]>o——–l<[Department]
A department can have more than one employee
In the following diagram, what type of relationship is depicted?
Ternary
A relationship between the instances of a single entity type is called a ________ relationship.
unary
In the following diagram, which of the answers below is true?
[Patient]-ll————-l<[Patient history]
Each patient has one or more patient histories.
A mutually exclusive relationship is one in which:
an entity instance can participate in only one of several alternative relationships
A ________ specifies the number of instances of one entity that can be associated with each instance of another entity.
cardinality constraint
The terms “data” and “information” mean essentially the same thing.
False
According to the lecture, the “meme” that is often used to describe the different levels of data needs was
“one person’s information is another person’s data.”
The term database refers to the software used to manage data.
False
Metadata is data that describes the properties or context of the actual data stored in the database.
True
According to the lecture, you can generally think of structured data as being able to be organized into rows and columns much like a spreadsheet.
True
According to the lecture, increased application development productivity is the most impactful advantage of relational databases over file processing systems.
False
According to the lecture, the relationship between a course and a section would be:
one-to-many
The logic required to read and write data in a file processing system is generally embedded directly into the program that must access that data.
True
The advantages of relational databases are so huge that they have effectively replaced file processing systems.
False
With relational databases, only the application that creates the data can access that data, a concept known as “maker-is-master data isolation.”
False
System developers do not write SQL to access relational databases, instead relying on specialized database administrators to perform this task.
False
Most databases that “back” the applications that we use on a daily basis are considered “operational” databases.
True
Dr. York occasionally wanted to “punch” which kind of project team member?
“Operational” Database Administrators
Modern (alternative) systems development processes have completely abandoned unnecessary development steps like planning, analysis, design and testing.
False
According to the lecture, eXtreme Programming and SCRUM are examples of Agile Methodologies.
True
SQL is a technical language that is intended to be used only by specialists.
False
One of the major limitations of personal databases is their lack of support for concurrent access by multiple users.
True
Enterprise application databases rarely mix data from different business functions (e.g., HR and Manufacturing).
False
According to the lecture, which of the following types of enterprise systems is often concerned with the administration of a manufacturing process.
Enterprise Resource Planning (ERP)
According to the lecture, an increased “volume and velocity” of data has been one of the primary forces driving the evolution of database technology.
True
In the context of a database, “E-R” is an acronym for:
Entity-Relationship
Although you need to learn how to model data for this course, as “hands-on” IT or Cybersecurity professionals, it’s highly unlikely that you’ll actually encounter them in the real world.
False
Data definitions are often assembled into a data dictionary within in a word processing document or spreadsheet file, not necessarily in a diagram or data modeling tool.
True
Business rules are captured using a very technical language that is understood only by application developers and data analysts.
False
Although there are numerous standards for notations, all E-R diagrams will model entities, attributes, relationships and the cardinality of the relationships.
True
According to the lecture, an “Entity Type” is most closely related to the concept of a(n) ________ in object-oriented programming.
Class
In general, a weak entity is less important than a strong entity, so we usually choose not to capture them.
False
When naming entities, it is best to be as concise as possible; this could even include abbreviation or acronyms if they are commonly referred to that way within an organization.
True
It is very common for a database have only a single Entity Instance for any given Entity Type.
False
Most of the time, it is neither necessary nor desirable to capture a system’s users (the person generating input) or outputs (screens, web pages, reports, etc.) in the database model.
True
If a composite identifier exists–even if it requires combining several fields–it is always desirable to use it instead of adding a surrogate identifier.
False
When designing a data model, it is important to group attributes together as composite attributes because databases always require you to enter them grouped this way.
False
Although a database cannot directly store multivalued attributes (i.e., attributes that can have zero or many individual values), it is important to capture these in your conceptual and logical data models.
True
Without exception, every entity stored in a database will need to be identified by a key (either simple, composite, or surrogate).
True
A course section requires three attributes to uniquely identify that section (semester, course_number, section_letter); this is a good example of a ______.
Composite Identifier
Even for a single database vendor, there are numerous acceptable standards for drawing ERD’s.
True
A ternary (or n-ary) relationship is a conceptual relationship between more than two tables in a diagram, but will not be directly modeled in the same way in a relational database.
True
When creating an ERD, it is vital to represent every possible conceptual relationship between two types of entities, even those not directly relevant to the problem domain.
False
Relationships between entities are always only unidirectional, meaning for example that you can only consider the relationship to be from entity A to entity B and not from B to A.
False
According to the lecture, the most common degree of relationship found in most database models is what?
Binary
According to the lecture, the ERD is the actual, underlying implementation of the database and it’s relationships (its “structure”), whereas the Data Model is simply a conceptual representation of this structure.
False
A high-school student is assigned a locker, and a locker can be assigned to only a single student at a time. This is an example of a ______ relationship.
One-to-One
An author can write many books and a book can have one or more authors. This is an example of a ______ relationship.
Many-to-many
Cardinality can also capture whether a relationship is optional or required.
True
One employee can work on many projects and one project can have many employees. This is an example of a ______ relationship.
Many-to-many
In the “crows-foot” ERD notation, the line or circle representing whether a relationship is mandatory or optional is the symbol closest to the box representing the entity type.
False
On a project, one employee can serve many roles. This is an example of a ______ relationship.
Insufficient Information to Determine the Correct Answer
Cardinality refers to the number of instances of one entity type that may conceivably be related to an instance of another entity type.
True
An airline flight can have only one pilot serving as Captain, but a pilot can be Captain on many flights. This is an example of a _______ relationship.
One-to-many
The primary purpose of an associative entity is to allow for a relational database to physically model a conceptual many-to-many relationship.
True
An attribute of an entity is considered “multivalued” because the entity will have just one of many possible values (e.g., a multiple-choice question with one right answer).
False
If a many-to-many relationship requires that we store attributes that further describe that relationship, those attributes should be stored in the associative entity.
True
A time stamp is distinct from other data types in that it only captures time (in a 24 hour UTC format), and not a date.
False
You do not need an associative entity if you are resolving a many-to-many unary relationship. They are only needed for binary relationships between separate entity types.
False
Strong Entity
A strong entity is a type of entity that doesn’t depend on any other entity in the database. It has a primary key attribute, which uniquely identifies each entity instance. Examples could be a Person, a Car, or a House.
Weak Entity
A weak entity depends on a strong entity to ensure its existence. It doesn’t have a primary key attribute of its own, so it uses a foreign key combined with some other attributes to create a composite primary key. These are typically items that are incompletely identified by their own attributes. For example, a ‘Classroom’ entity might be weak if its existence depends on a ‘School’ entity.
Associative Entity (also known as a linking or bridge entity)
This is often used to link many-to-many relationships. It consists of one or more foreign keys, each coming from the entities being connected. Sometimes, associative entities also contain additional attributes that provide more information about the relationship. For instance, if ‘Students’ and ‘Courses’ are entities, an ‘Enrollment’ associative entity might link them and contain extra data like ‘dateEnrolled’ or ‘finalGrade’.
Derived Entity
This type of entity is one whose attributes are derived from other entities in the database. For example, an ‘Invoice’ entity might be derived from a ‘Purchase’ entity and a ‘Customer’ entity.
Subtype and Supertype Entities
In certain scenarios, entities are organized into hierarchies. A supertype is a generic entity type that has a relationship with one or more subtype entities. These subtype entities inherit the attributes and relationships of the supertype. For instance, a ‘Vehicle’ supertype could have ‘Car’, ‘Bicycle’, and ‘Motorcycle’ subtypes.
Abstract Entity
This entity captures common characteristics of certain entities, but it doesn’t usually exist on its own. It’s used for data modeling to simplify definitions and avoid redundancy. It’s more commonly used in Object-Oriented Database Management Systems.
Inner Join
This is the most common type of join. It returns records that have matching values in both tables involved in the join. If a record in the first table doesn’t have a corresponding record in the second table, it is excluded from the result set (and vice versa).
Left outer join (or left join)
This returns all records from the left table (the first table), and the matched records from the right table (the second table). The result is NULL in the right side when there is no match.
Right outer join (or right join)
This returns all records from the right table, and the matched records from the left table. The result is NULL in the left side when there is no match.
Full outer join (or full join)
This returns all records when there is a match in one of the tables. Therefore, it returns all the records from both tables with NULL in either side when there isn’t a match. Not all database systems support full outer joins natively, but they can typically be emulated using a union of left and right joins.
Natural Join
A natural join is a type of join that implies an implicit equality condition. It performs an equi-join based on all columns with the same name in both tables being joined. The result set only includes one column for each pair of equally named columns. Most database experts advise against using natural joins, as they can lead to unexpected results, especially if the table schemas change over time. They also lack explicitness, which can make the SQL harder to understand.
Cross Join
a cross join is worth noting. It returns the Cartesian product of the two tables involved, meaning every row of the first table is joined to every row of the second table. This type of join can produce very large result sets and is rarely used in practice without a limiting WHERE clause.
Remember, the “left” and “right” designations in the join types refer to the order of the tables as they are listed in the SQL statement. The “left” table is the one that appears first, while the “right” table appears second.
Who invented the relational model?
The relational model for database management is a database model that was invented by E.F. Codd, a British computer scientist, while working for IBM. He introduced the concept in his seminal 1970 paper titled “A Relational Model of Data for Large Shared Data Banks,” which was published in the journal Communications of the ACM. This model became the theoretical basis for relational databases, changing how databases were constructed and used across numerous applications and industries.
