Podcast
Questions and Answers
Which of the following best describes the primary purpose of the Entity Relationship Model (ERM)?
Which of the following best describes the primary purpose of the Entity Relationship Model (ERM)?
- To implement data security and access controls.
- To optimize query performance in a relational database.
- To illustrate relationships among entities at a conceptual level. (correct)
- To define the physical storage structures of a database.
In an Entity Relationship Diagram (ERD), how is an entity typically represented?
In an Entity Relationship Diagram (ERD), how is an entity typically represented?
- Diamond
- Rectangle (correct)
- Oval
- Circle
What term describes a specific instance or occurrence of an entity within the Entity Relationship Model (ERM)?
What term describes a specific instance or occurrence of an entity within the Entity Relationship Model (ERM)?
- Entity set
- Relationship
- Entity Instance (correct)
- Attribute
In ER modeling, what does 'connectivity' refer to?
In ER modeling, what does 'connectivity' refer to?
In the Chen notation for ER diagrams, how are relationships represented?
In the Chen notation for ER diagrams, how are relationships represented?
In the context of ER diagrams, what does cardinality express?
In the context of ER diagrams, what does cardinality express?
What is the purpose of attributes in an Entity Relationship Model (ERM)?
What is the purpose of attributes in an Entity Relationship Model (ERM)?
In the original Chen notation, how are attributes represented in an ER diagram?
In the original Chen notation, how are attributes represented in an ER diagram?
In the Crow's Foot notation, how are mandatory or required attributes typically indicated?
In the Crow's Foot notation, how are mandatory or required attributes typically indicated?
What is the purpose of underlining an attribute in an ER diagram?
What is the purpose of underlining an attribute in an ER diagram?
What is the term for raw data in its original state, which may contain redundancies and other data anomalies?
What is the term for raw data in its original state, which may contain redundancies and other data anomalies?
What is a data anomaly in the context of database management?
What is a data anomaly in the context of database management?
Which of the following best describes the process of normalization in database design?
Which of the following best describes the process of normalization in database design?
Which of the following is a primary objective of normalization?
Which of the following is a primary objective of normalization?
What is a key characteristic of a table that is in First Normal Form (1NF)?
What is a key characteristic of a table that is in First Normal Form (1NF)?
What is the defining characteristic of Second Normal Form (2NF)?
What is the defining characteristic of Second Normal Form (2NF)?
What condition does Third Normal Form (3NF) satisfy beyond the requirements of 2NF?
What condition does Third Normal Form (3NF) satisfy beyond the requirements of 2NF?
What does Boyce-Codd Normal Form (BCNF) ensure?
What does Boyce-Codd Normal Form (BCNF) ensure?
What additional condition does Fourth Normal Form (4NF) address beyond the requirements of 3NF?
What additional condition does Fourth Normal Form (4NF) address beyond the requirements of 3NF?
Up to which normal form is considered the highest level necessary for most applications?
Up to which normal form is considered the highest level necessary for most applications?
In the context of database normalization, what is a 'nonprime attribute'?
In the context of database normalization, what is a 'nonprime attribute'?
Which of the following is a characteristic of a well-normalized database table?
Which of the following is a characteristic of a well-normalized database table?
Consider a database table where an employee's name can determine their department. Which normal form is violated if this dependency exists and the department is not determined by the primary key?
Consider a database table where an employee's name can determine their department. Which normal form is violated if this dependency exists and the department is not determined by the primary key?
In a database table, a student can have multiple majors. If the table is not in 4NF, what kind of dependency exists?
In a database table, a student can have multiple majors. If the table is not in 4NF, what kind of dependency exists?
Considering the tables 'Advisers', 'Subjects', 'Students', and 'StudentAdvisers', what is the primary key of the 'StudentAdvisers' table?
Considering the tables 'Advisers', 'Subjects', 'Students', and 'StudentAdvisers', what is the primary key of the 'StudentAdvisers' table?
Why is it important for each table to represent a single subject in a normalized database?
Why is it important for each table to represent a single subject in a normalized database?
Which normal form aims to remove redundancy that arises because of transitive functional dependencies?
Which normal form aims to remove redundancy that arises because of transitive functional dependencies?
What type of database anomaly is most directly addressed by normalizing a database from 1NF to 2NF?
What type of database anomaly is most directly addressed by normalizing a database from 1NF to 2NF?
Which normal form explicitly requires that every determinant in a table be a candidate key?
Which normal form explicitly requires that every determinant in a table be a candidate key?
If a table is in 3NF but not in BCNF, what type of situation most likely exists?
If a table is in 3NF but not in BCNF, what type of situation most likely exists?
Consider a relation EMPLOYEE(empID, projectName, salary). An employee can work on multiple projects. Is this relation in 3NF? If not, why?
Consider a relation EMPLOYEE(empID, projectName, salary). An employee can work on multiple projects. Is this relation in 3NF? If not, why?
What problem arises if a database table isn't normalized and contains redundant data?
What problem arises if a database table isn't normalized and contains redundant data?
Why is 3NF often considered a sufficient level of normalization for many practical database applications?
Why is 3NF often considered a sufficient level of normalization for many practical database applications?
What is the significance of a 'determinant' in the context of database normalization?
What is the significance of a 'determinant' in the context of database normalization?
In database design, what does the term 'functional dependency' mean?
In database design, what does the term 'functional dependency' mean?
Consider a table ORDER (orderID, customerID, customerName, productID, productName). If customerID determines customerName and productID determines productName, what normal form does this violate?
Consider a table ORDER (orderID, customerID, customerName, productID, productName). If customerID determines customerName and productID determines productName, what normal form does this violate?
Consider a table PROJECT(projectID, employeeID, taskID, hoursWorked). If an employee can work on multiple tasks within a project, what is the most likely primary key?
Consider a table PROJECT(projectID, employeeID, taskID, hoursWorked). If an employee can work on multiple tasks within a project, what is the most likely primary key?
What is the primary goal of normalizing a database schema?
What is the primary goal of normalizing a database schema?
Which of the following normal forms deals with the issue of transitive dependencies?
Which of the following normal forms deals with the issue of transitive dependencies?
Flashcards
Entity Relationship Model (ERM)
Entity Relationship Model (ERM)
A data model describing relationships among entities at a conceptual level, using ER diagrams.
Entity Relationship Diagram (ERD)
Entity Relationship Diagram (ERD)
A diagram visually representing an ER model's entities, attributes, and relationships.
Entity (in ERD)
Entity (in ERD)
A rectangle representing a real-world object or concept in an ERD.
Entity Instance
Entity Instance
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Entity Set
Entity Set
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Relationship (in ERD)
Relationship (in ERD)
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Connectivity (in ERD)
Connectivity (in ERD)
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Attributes
Attributes
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Unnormalized Data
Unnormalized Data
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Data anomaly
Data anomaly
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Normalization
Normalization
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Atomic Attribute
Atomic Attribute
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First Normal Form (1NF)
First Normal Form (1NF)
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Second Normal Form (2NF)
Second Normal Form (2NF)
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Third Normal Form (3NF)
Third Normal Form (3NF)
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Study Notes
- Entity Relationship Model (ERM) is a data model that uses ER diagrams to describe relationships among entities at the conceptual level
- Entity Relationship Diagram (ERD) depicts an entity relationship model's entities, attributes, and relations
- An entity is represented in an ERD by a rectangle, also known as an entity box, where the entity's name (a noun) is written in the center in capital letters and singular form
- Each row in the relational table is known as an entity instance or entity occurrence in the ER model
- A collection of similar entities is known as an entity set
- Relationships describe associations among data
- Connectivity is the type of relationship between entities represented by a line in an ERD
- The relationship name is usually an active or passive verb
ER Model Notations
- Chen notation represents relationships through a diamond connected to the related entities through a line, with the relationship name inside the diamond
- Crow's Foot notation connects entities by lines, and symbols at either end describe the cardinality of the relationship between entities
Attributes
- Each entity has a set of attributes describing particular characteristics
- In Chen notation, attributes are represented by ovals connected to the entity rectangle, each containing the attribute name, and the entity identifier is mapped as the table's primary key and underlined
- In Crow's Foot notation, attributes are written in the attribute box; required attributes are in boldface, and PK/FK denote primary/foreign keys
Normalization
- Unnormalized data is raw and may contain redundant/multivalued data/data anomalies, where a data anomaly is an undesirable consequence of a data modification
- Normalization assigns attributes to entities to reduce or eliminate data redundancies; the objectives are:
- Each table/relation represents a single subject
- Each row/column intersection contains only one value
- No data item is unnecessarily stored in more than one table
- Nonprime attributes depend on the primary key
- Each table has no insertion, update, or deletion anomalies
- Each rule in database normalization is called a normal form
Common Normal Forms
- First normal form (1NF): No repeating groups, and the primary key is identified
- Second normal form (2NF): 1NF plus all columns depend on the table's primary key
- Third normal form (3NF): 2NF plus no non-key attributes determined by another non-key attribute
- Boyce-Codd normal form (BCNF): Every determinant is a candidate key (special case of 3NF)
- Fourth normal form (4NF): 3NF and no independent multivalued dependencies
- 3NF is considered the highest level necessary for most applications
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