SQL (Structured Query Language) is a powerful programming language designed for managing and manipulating relational databases. It is widely used in various industries to handle data operations, including querying, updating, and managing data stored in relational database management systems (RDBMS).

Data Definition Language (DDL):

CREATE: Defines new database objects such as tables, views, and indexes.

ALTER: Modifies existing database objects.

DROP: Deletes existing database objects.

Data Manipulation Language (DML):

SELECT: Retrieves data from one or more tables.

INSERT: Adds new rows of data to a table.

UPDATE: Modifies existing data within a table.

DELETE: Removes data from a table.

Data Control Language (DCL):

GRANT: Provides users with access privileges to the database.

REVOKE: Removes user access privileges.

Transaction Control Language (TCL):

COMMIT: Saves all changes made during the transaction.

ROLLBACK: Reverts all changes made during the transaction.

SAVEPOINT: Sets a point within a transaction to which you can later roll back.

Joins:

Combine rows from two or more tables based on a related column.

Types include INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL OUTER JOIN.

Indexes:

Improve the speed of data retrieval operations.

Can be created on one or more columns of a table.

Views:

Virtual tables created by a query.

Simplify complex queries and provide data security.

Normalization:

Process of organizing data to minimize redundancy.

Includes various normal forms (1NF, 2NF, 3NF, etc.).

Subqueries:

Nested queries used within another SQL query.

Useful for complex filtering and data manipulation.

Aggregate Functions:

Perform calculations on multiple rows of a table's column and return a single value.

Includes COUNT, SUM, AVG, MIN, and MAX.

Constraints:

Rules enforced on data columns to ensure data integrity.

Types include PRIMARY KEY, FOREIGN KEY, UNIQUE, NOT NULL, and CHECK.

SQL Functions:

Built-in functions for performing calculations, string manipulations, date-time processing, and more.

Includes functions like CONCAT, SUBSTRING, DATEADD, and CAST.

Stored Procedures and Triggers:

Stored Procedures: Precompiled collections of SQL statements stored under a name and executed as a unit.

Triggers: Automatically executed commands in response to specific events on a table or view.

Security:

User authentication and authorization mechanisms.

Control over access to data and database objects.

Data Integrity:

Ensuring accuracy and consistency of data over its lifecycle.

Includes enforcing constraints, transactions, and normalization practices.