1. Relational Database Management System (RDBMS)

Definition: An RDBMS is a type of database management system (DBMS) that stores data in a structured format, using rows and columns. It provides a way to manage and manipulate data using SQL (Structured Query Language). The "relational" part comes from the fact that the data is organized into tables that can be related to each other.

Key Concepts:

• Tables: The basic building blocks of an RDBMS. Each table consists of rows (records) and columns (attributes).
• Schemas: The structure of a database, including tables, columns, data types, and relationships. Schemas define how data is organized and how the tables relate to one another.
• Primary Keys: A unique identifier for each record in a table. This ensures that each record can be uniquely identified.
• Foreign Keys: Attributes in one table that reference the primary key in another table. This establishes relationships between tables.
• Normalization: The process of organizing data to reduce redundancy and improve data integrity. It involves dividing tables into smaller, related tables and defining relationships between them.

2. SQL (Structured Query Language)

SQL is the language used to interact with an RDBMS. It allows you to create, read, update, and delete data. SQL is divided into several categories:

Data Definition Language (DDL):

• CREATE: Used to create new tables, views, indexes, or databases.
• ALTER: Used to modify the structure of an existing database object, such as a table.
• DROP: Used to delete database objects like tables or indexes.

Data Manipulation Language (DML):

• SELECT: Retrieves data from one or more tables.
• INSERT: Adds new records to a table.
• UPDATE: Modifies existing records in a table.
• DELETE: Removes records from a table.

Data Control Language (DCL):

• GRANT: Provides specific privileges to users.
• REVOKE: Removes specific privileges from users.

Transaction Control Language (TCL):

• COMMIT: Saves all changes made during the current transaction.
• ROLLBACK: Undoes changes made during the current transaction.
• SAVEPOINT: Sets a point within a transaction to which you can later roll back.

3. Key Concepts in SQL

Queries:

• SELECT Statement: Retrieves data from a database.
  sql code
  SELECT column1, column2 FROM table_name WHERE condition

Joins:

• INNER JOIN: Returns rows when there is a match in both tables.
• LEFT JOIN (or LEFT OUTER JOIN): Returns all rows from the left table and matched rows from the right table.
• RIGHT JOIN (or RIGHT OUTER JOIN): Returns all rows from the right table and matched rows from the left table.
• FULL JOIN (or FULL OUTER JOIN): Returns rows when there is a match in one of the tables.

Indexes:

• Indexes: Improve the speed of data retrieval operations on a table. They are created on columns that are frequently used in queries.

Views:

• Views: Virtual tables created by a query. They don’t store data themselves but provide a way to simplify complex queries or present data in a specific format.

Transactions:

• Transactions: A sequence of SQL operations performed as a single logical unit of work. Transactions ensure that all operations within the transaction are completed successfully before committing them to the database.

Constraints:

• NOT NULL: Ensures that a column cannot have a NULL value.
• UNIQUE: Ensures all values in a column are unique.
• CHECK: Ensures that values in a column meet a specific condition.
• DEFAULT: Provides a default value for a column when no value is specified.
• PRIMARY KEY: Uniquely identifies each record in a table.
• FOREIGN KEY: Ensures referential integrity by linking records between tables.

4. Normalization

Normalization involves organizing data to minimize redundancy and dependency. The process usually involves several normal forms (NF):

• First Normal Form (1NF): Ensures that the table has a primary key and that all columns contain atomic (indivisible) values.
• Second Normal Form (2NF): Builds on 1NF by ensuring that all non-key attributes are fully functionally dependent on the entire primary key.
• Third Normal Form (3NF): Ensures that all attributes are only dependent on the primary key and not on other non-key attributes.
• Boyce-Codd Normal Form (BCNF): A stricter version of 3NF.
• Fourth Normal Form (4NF): Deals with multi-valued dependencies.
• Fifth Normal Form (5NF): Deals with join dependencies.

5. Database Design and Relationships

• One-to-One Relationship: A single record in one table is related to a single record in another table.
• One-to-Many Relationship: A single record in one table is related to multiple records in another table.
• Many-to-Many Relationship: Multiple records in one table are related to multiple records in another table, typically managed through a junction table.

6. Advanced Topics

• Stored Procedures: Predefined SQL code that can be executed on demand. They help in reusing SQL code and improving performance.
• Triggers: Automatically execute SQL code in response to certain events on a table or view, such as insert, update, or delete operations.
• Views and Materialized Views: Views are virtual tables, while materialized views store the query results physically for performance improvement.

7. Performance Tuning

• Query Optimization: Techniques to improve the performance of SQL queries, including indexing, query rewriting, and analyzing execution plans.
• Database Indexing: Creating indexes to speed up data retrieval operations.
• Caching: Storing frequently accessed data in a temporary storage to reduce retrieval time.

Understanding these concepts will give you a solid foundation in working with SQL and relational databases. If you have any specific questions or need further details on any of these topics, feel free to ask!