Introduction to Databases Flashcards
What do DBMS comprise of
- Collection of interrelated data
- A set of programs to access the data
- An environment convenient and efficient
What are the drawbacks of filesystems over Databases?
- Data redundancy and inconsistency
- Difficult to access
- Data Isolation
- Integrity problems
- Atomicity of Updates
- Concurrent Access
- Security
What does data integrity mean?
Data integrity refers to the accuracy, consistency, and reliability of data throughout its entire lifecycle. It ensures that data remains unchanged during storage, transmission, or processing and that it is reliable for use. Maintaining data integrity is crucial in various fields, including databases, information systems, and data storage.
What is data inconsistency?
Data inconsistency refers to a situation in which the same piece of data is stored in multiple locations or instances within a system, and these copies of the data become out of sync or contradictory. Inconsistencies can arise from various factors, such as software bugs, human errors, system failures, or issues with data synchronization
What are the benefits of Electronic Record Keeping as against Physical Record Keeping?
- Durability
- Scalability
- Security
- Retrieval
- Ease of Use
- Consistency
- Efficiency
- Cost
Where does a File System perform better than a DBMS?
- File Handling
- Initial Setup
- Arithmetic and logical operations support
What is data robustness?
Data robustness refers to the ability of a system or dataset to maintain its stability, integrity, and functionality in the face of adverse conditions, errors, or unexpected events. A system with high data robustness can handle disruptions, errors, or changes without experiencing a significant loss of performance or reliability.
What are the levels of abstraction in DBMS?
- Physical Level
- Logical Level
- View Level
What is a logical schema?
the overall logical structure of the database analogous to “type” information of a variable in a program
What is an instance of a database?
The actual content of the database at a particular point in time, is analogous to the value of a variable.
What is Physical Data Independence?
Physical Data Independence is the ability to modify the physical schema without
changing the logical schema
What are the types of Data Models?
- Relational Model (RDBMS)
- Object-Oriented Model
- Network Model
- Hierarchical Model
How are data stored in the Relational Model?
Data is stored as tables in Relational Model
What is a Data Dictionary?
The data dictionary contains metadata (that is, data about data)
◦ Database schema
◦ Integrity constraints - Primary key (ID uniquely identifies instructors)
◦ Authorization
What is Data Definition Language (DDL)?
Specification notation for defining the database schema. DDL compiler generates a set of table templates stored in a data dictionary
What is Data Manipulation Language (DML)?
Language for accessing and manipulating the data organized by the appropriate data
model. DML is also known as Query Language.
What are the two classes of languages of DML?
◦ Pure – used for proving properties about computational power and for optimization
. Relational Algebra (we focus in this course)
. Tuple relational calculus
. Domain relational calculus
◦ Commercial – used in commercial systems
. SQL is the most widely used commercial language
What are the parts of a Database Engine?
- Storage manager
- Query processing
- Transaction manager
What is the function of the “storage manager” of a database engine?
- Storage manager is a program module that provides the interface between the
low-level data stored in the database and the application programs and queries
submitted to the system - The storage manager is responsible for the following tasks:
◦ Interaction with the OS file manager
◦ Efficient storing, retrieving, and updating of data - Issues:
◦ Storage Access
◦ File organization
◦ Indexing and hashing
What is the function of the “Query Processor” of a database engine?
a) Parsing and translation
b) Optimization
c) Evaluation
- Alternative ways of evaluating a given query
◦ Equivalent expressions
◦ Different algorithms for each operation - The cost difference between a good and a bad way of evaluating a query can be enormous
- Need to estimate the cost of operations
◦ Depends critically on statistical information about relations which the database
must maintain
◦ Need to estimate statistics for intermediate results to compute the cost of complex
expressions
What is the function of the “Transaction Management” of a database engine?
A transaction is a collection of operations that performs a single logical function in a
database application
Transaction-management component ensures that the database remains in a
consistent (correct) state despite system failures (e.g., power failures and operating
system crashes) and transaction failures.
* Concurrency-control manager controls the interaction among the concurrent
transactions, to ensure the consistency of the database.
What are the different types of Database Architecture?
- Centralized
- Client-server
- Parallel (multi-processor)
- Distributed
- Cloud
Types of Database Users
- Naive Users
- Application Users
- Sophisticated Users (analysts)
- Database Administrators
What are the main components of a database?
- Hardware
- Software
- Users
- Data Models
- Stored Procedures and Triggers
- Security and Access Control
