1. Database
Definition:
A database is a structured collection of data stored and managed electronically. It allows for efficient data retrieval, manipulation, and management.
Characteristics:
- Structured: Data is organized in tables with rows and columns.
- Persistent: Data remains available over time.
- Accessible: Allows querying and manipulation through a Database Management System (DBMS).
2. Database Management System (DBMS)
Definition:
A DBMS is software that facilitates the creation, manipulation, and management of databases. It provides an interface for users and applications to interact with the data.
Characteristics:
- Data Definition: Allows creation and modification of database schemas.
- Data Manipulation: Supports querying, updating, and deleting data.
- Data Security: Manages user access and data integrity.
3. Table (Relation)
Definition:
A table, also known as a relation, is a collection of rows and columns used to store data in a relational database.
Characteristics:
- Rows: Each row represents a single record or entity.
- Columns: Each column represents an attribute of the entity.
- Schema: Defines the structure, including column names and data types.
4. Row (Tuple)
Definition:
A row, or tuple, represents a single record in a table. It is a set of related data values corresponding to the columns of the table.
Characteristics:
- Unique: Each row represents a unique instance of the entity.
- Data Integrity: Must conform to the table schema.
5. Column (Attribute)
Definition:
A column, or attribute, represents a data field in a table. It defines a specific type of data that each row in the table can hold.
Characteristics:
- Data Type: Specifies the kind of data stored, such as integer, text, or date.
- Constraints: Includes rules such as NOT NULL or UNIQUE.
6. Primary Key
Definition:
A primary key is a unique identifier for each record in a table. It ensures that no two rows have the same key value and cannot be NULL.
Characteristics:
- Uniqueness: Guarantees that each record can be uniquely identified.
- Non-nullable: Cannot have NULL values.
- Single Key: Each table can have only one primary key.
7. Foreign Key
Definition:
A foreign key is a column or set of columns in one table that uniquely identifies a row in another table. It establishes a relationship between two tables.
Characteristics:
- Referential Integrity: Ensures that the value in the foreign key column matches a value in the primary key of the referenced table.
- Nullable: Can accept NULL values, indicating optional relationships.
8. Unique Key
Definition:
A unique key ensures that all values in a column or a set of columns are distinct from one another across the table.
Characteristics:
- Uniqueness: No two rows can have the same value for the unique key column(s).
- Nullable: Unlike primary keys, unique keys can have NULL values.
9. Index
Definition:
An index is a database object that improves the speed of data retrieval operations on a table at the cost of additional storage and maintenance overhead.
Characteristics:
- Speed: Enhances query performance by allowing quicker searches.
- Types: Includes unique, composite, and full-text indexes.
- Maintenance: Indexes need to be updated when the table data changes.
10. Schema
Definition:
A schema is the structure of a database, including tables, columns, data types, relationships, and constraints.
Characteristics:
- Design: Defines the organization and design of the database.
- Documentation: Provides a blueprint for database creation and modification.
11. Normalization
Definition:
Normalization is the process of organizing data to reduce redundancy and improve data integrity. It involves dividing a database into two or more tables and defining relationships between them.
Characteristics:
- Normal Forms: Includes First Normal Form (1NF), Second Normal Form (2NF), Third Normal Form (3NF), and Boyce-Codd Normal Form (BCNF).
- Reduction of Redundancy: Eliminates duplicate data.
- Dependency: Ensures that data dependencies are logical.
12. Denormalization
Definition:
Denormalization is the process of combining tables to improve read performance at the cost of increased redundancy and potential write anomalies.
Characteristics:
- Performance: Enhances query performance by reducing the number of joins needed.
- Redundancy: Introduces some level of data duplication.
13. Query
Definition:
A query is a request for data or information from a database using a query language, such as SQL (Structured Query Language).
Characteristics:
- Data Retrieval: Allows users to select and display data from one or more tables.
- Data Manipulation: Includes INSERT, UPDATE, and DELETE operations.
14. Transaction
Definition:
A transaction is a sequence of one or more SQL operations executed as a single unit of work. Transactions ensure that operations are completed successfully or not executed at all.
Characteristics:
- ACID Properties: Ensures Atomicity, Consistency, Isolation, and Durability.
- Commit/Rollback: Either commits all changes or rolls back to the previous state if an error occurs.
15. View
Definition:
A view is a virtual table based on the result of a query. It provides a way to present data in a particular format without storing it separately.
Characteristics:
- Virtual Table: Does not store data physically but displays data from underlying tables.
- Security: Restricts user access to specific data.
Quick Recap:
- Database: Structured data storage.
- DBMS: Software for managing databases.
- Table (Relation): Collection of rows and columns.
- Row (Tuple): Single record in a table.
- Column: Data field in a table.
- Primary Key: Unique identifier for records.
- Foreign Key: Links tables.
- Unique Key: Ensures distinct values.
- Index: Speeds up data retrieval.
- Schema: Database structure.
- Normalization: Reduces redundancy.
- Denormalization: Enhances performance.
- Query: Request for data.
- Transaction: Group of operations.
- View: Virtual table for data presentation.
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