Podcast
Questions and Answers
Which of these is a characteristic of a weak entity?
Which of these is a characteristic of a weak entity?
- It has a primary key.
- It is always represented by a double rectangle.
- It is used to model one-to-one relationships.
- It depends on a strong entity for its existence. (correct)
Which of the following is an example of a many-to-many relationship?
Which of the following is an example of a many-to-many relationship?
- A student can involve into multiple causes. (correct)
- A scientist can invent an invention. (correct)
- A male can marry a female.
- A teacher can teach multiple students.
Which data model is best suited for representing many-to-many relationships?
Which data model is best suited for representing many-to-many relationships?
- Network data model
- Hierarchical data model
- Entity Relationship model (correct)
- Object-based data model
What is an example of a derived attribute?
What is an example of a derived attribute?
Which of these data modeling techniques is NOT directly related to managing many-to-many relationships?
Which of these data modeling techniques is NOT directly related to managing many-to-many relationships?
What is the difference between a key attribute and a composite attribute?
What is the difference between a key attribute and a composite attribute?
Which application domain would you use the ER model for?
Which application domain would you use the ER model for?
Which of the following is NOT a benefit of using a data model in a Database Management System (DBMS)?
Which of the following is NOT a benefit of using a data model in a Database Management System (DBMS)?
Which type of constraint ensures that a column cannot contain duplicate values?
Which type of constraint ensures that a column cannot contain duplicate values?
What is the purpose of a Foreign Key Constraint?
What is the purpose of a Foreign Key Constraint?
Which constraint is used to define a default value for a column?
Which constraint is used to define a default value for a column?
What is the primary purpose of handling null values in a database?
What is the primary purpose of handling null values in a database?
In the context of a relational database, what is a row also known as?
In the context of a relational database, what is a row also known as?
What is the primary purpose of normalization in a relational database?
What is the primary purpose of normalization in a relational database?
Which of the following scenarios is NOT a valid reason for de-normalization?
Which of the following scenarios is NOT a valid reason for de-normalization?
Which of the following is a key component of the relational model?
Which of the following is a key component of the relational model?
Which of these scenarios best describes a ternary relationship?
Which of these scenarios best describes a ternary relationship?
What is the difference between a conceptual schema and a physical schema?
What is the difference between a conceptual schema and a physical schema?
Which of the following is NOT a component of the database blueprint structure?
Which of the following is NOT a component of the database blueprint structure?
Which of the following best describes a logical level data?
Which of the following best describes a logical level data?
In an ER model, what is the difference between an entity and an attribute?
In an ER model, what is the difference between an entity and an attribute?
Which of the following is NOT a characteristic of a hard disk database?
Which of the following is NOT a characteristic of a hard disk database?
Which of the following is an example of an aggregation relationship?
Which of the following is an example of an aggregation relationship?
What is the purpose of logical to physical mapping?
What is the purpose of logical to physical mapping?
Flashcards
Entity
Entity
An object class or person represented in the ER model.
Attribute
Attribute
A property or characteristic of an entity.
Key Attribute
Key Attribute
A unique identifier for an entity, such as ID.
Composite Attribute
Composite Attribute
An attribute that combines multiple values, such as a full name.
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Weak Entity
Weak Entity
An entity that depends on a strong entity for its identification.
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Derived Attribute
Derived Attribute
An attribute that can be calculated from other attributes, like age from birth date.
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One to Many Relationship
One to Many Relationship
A relationship where one entity can relate to multiple instances of another entity.
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Many to Many Relationship
Many to Many Relationship
A relationship where multiple instances of an entity can relate to multiple instances of another entity.
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Schema
Schema
The structure or blueprint of a database.
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External Schema
External Schema
The view schema that allows users to interact with the database.
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Conceptual Schema
Conceptual Schema
The overall logical structure of the database, independent of physical implementation.
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Physical Schema
Physical Schema
Defines how data is actually stored and accessed in the database.
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Entity vs Attribute
Entity vs Attribute
An entity is a distinguishable object, while attributes are its characteristics.
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Binary Relationship
Binary Relationship
A relationship involving two entities.
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Ternary Relationship
Ternary Relationship
A relationship that involves three entities.
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Aggregation in ER Model
Aggregation in ER Model
A type of relationship treated as an entity.
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Primary Key
Primary Key
Uniquely identifies each record in a table.
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Foreign Key
Foreign Key
Ensures that data in one table matches data in another table.
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Unique Constraint
Unique Constraint
Ensures that all values in a column are unique.
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Not Null Constraint
Not Null Constraint
Ensures that a column cannot contain null values.
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Check Constraint
Check Constraint
Ensures that data in a column meets specific criteria.
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Default Constraint
Default Constraint
Specifies a default value for a column.
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Data Integrity
Data Integrity
Maintaining accuracy and consistency of data in a database.
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Normalization
Normalization
Optimizing a database design to reduce redundancy and improve data integrity.
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Database Architecture
- Three levels of abstraction in database schema structure
- External Schema (View Schema/Sub Schema): Users interact with the database through external schemas, providing specific views of the database
- Conceptual Schema: This is the logical design of the database, representing entities and attributes and their relationships
- Physical Schema: This level specifies how the data is physically stored on the hard disk
- Abstract levels, each with data indepence
Data Storage and Access Paths
- Data storage: The data is physically stored in the hard disk database
- Access paths: The mapping between the conceptual and physical level is called conceptual/physical mapping, showing how data is accessed
- Database blueprints are the structure of the database
Entity Relationship Diagram (ERD)
- ER diagrams (entity-relationship diagrams) are used to visualize the design of databases
- Entities are objects (subjects) with unique attributes, represented by rectangles
- Attributes are characteristics or properties related to entities, represented by oval shapes
- Relationships show the connection/link between entities using diamonds
- Binary vs Ternary relationship: Entities that connect to two or more entities is tertiary, which is represented as a three-way relationship
Database Design and Entities
- Entities/attributes define the structure
- Database applications: businesses, healthcare, financial, education, government, social media, scientific, and engineering communities use databases
- Design with ER model/additional features
- Entity-Relationship model
Data Models in DBMS
- Hierarchical
- Network
- Relational
- Object-based
- Semi-structured
Constraints in Relational Model
- Constraints in a relational database to maintain data integrity and consistency
Primary and Foreign Keys
- Primary keys: Unique identifiers in a table
- Foreign keys: Relationships between tables through a common attribute/column
Unique Constraints
- Uniqueness of data value in a column
Not Null Constraints
- Data cannot be null in a given attribute/column
Check Constraints
- Ensuring values meet specific criteria
Default Constraints
- Assigning default values in a column
Null Values
- Importance of handling null values
- Handling data inconsistency and improving data accuracy
Relational Algebra
- Procedural language for manipulating relational databas, using
- Operations: selection, projection, union, intersection, difference, cartesian product, join
Relational Calculus
- Declarative language for expressing queries for relational databases, using domain and tuple variables
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