What is a SQL explain? What SQL is used? What are the languages of SQL?

SQL (Structured Query Language) is a standard programing language specifically designed for managing and manipulating relational databases.

Features of SQL

Data Definition Language (DDL):
- CREATE: To create databases and database objects like tables, indexes.
- ALTER: To modify existing database structures.
- DROP: To delete databases and database objects.
Data Manipulation Language (DML):
- SELECT: To query data from a database.
- INSERT: To insert data into tables.
- UPDATE: To update existing data.
- DELETE: To delete records.
Data Control Language (DCL):
- GRANT: To provide access or privileges to users.
- REVOKE: To remove access or privileges.
Transaction Control Language (TCL):
- COMMIT: To save the work done.
- ROLLBACK: To undo the work done.
- SAVEPOINT: To set a savepoint within a transaction.
- SET TRANSACTION: To specify characteristics for the transaction.
Built-in Functions:
- Aggregate functions like COUNT, SUM, AVG.
- Scalar functions like UPPER, LOWER, NOW.
Joins:
- INNER JOIN, LEFT JOIN, RIGHT JOIN, FULL JOIN, etc., to combine records from multiple tables.
Views:
- Virtual tables created by querying one or more tables.
Indexes:
- Performance optimization features to speed up data retrieval.
Stored Procedures and Functions:
- Reusable SQL code blocks for complex operations.
Subqueries and Nested Queries:
- Queries within queries for complex data retrieval.

High Speed:
- SQL queries can retrieve large amounts of data efficiently.
Well-defined Standards:
- SQL is an ANSI and ISO standard, ensuring consistency and reliability.
Portability:
- SQL can be used across different platforms, systems, and devices.
Interactive Language:
- SQL allows for direct interaction with databases using a straightforward command structure.
Multiple Data Views:
- SQL can create different views of the database structure for different users.
Integration:
- SQL integrates well with various programming languages and database management systems.
Robust Transaction Control:
- Ensures data integrity and consistency with features like COMMIT, ROLLBACK, and SAVEPOINT.
Security:
- Provides fine-grained access control through DCL commands.
Reduced Coding:
- Simplifies complex data manipulations with concise queries.
Scalability:

SQL is used for:

Querying Data:
- Retrieving specific data from one or more tables using the SELECT statement.
Updating Data:
- Modifying existing data in the database using the UPDATE statement.
Inserting Data:
- Adding new records to a table using the INSERT INTO statement.
Deleting Data:
- Removing records from a table using the DELETE statement.
Creating and Modifying Database Structures:
- Creating new tables, indexes, and views using the CREATE statement.
- Modifying existing database objects using the ALTER statement.
- Dropping database objects using the DROP statement.
Controlling Access to Data:
- Granting and revoking user permissions using GRANT and REVOKE statements.
Managing Transactions:
- Ensuring data integrity and consistency using COMMIT, ROLLBACK, and SAVEPOINT statements.

SQL is divided into several sublanguages, each with specific purposes:

Data Definition Language (DDL):
- Used to define and manage database structures.
- Key Commands: CREATE, ALTER, DROP, TRUNCATE
Data Manipulation Language (DML):
- Used to manage data within database objects.
- Key Commands: SELECT, INSERT, UPDATE, DELETE
Data Control Language (DCL):
- Used to control access to data in the database.
- Key Commands: GRANT, REVOKE
Transaction Control Language (TCL):
- Used to manage transactions within the database.
- Key Commands: COMMIT, ROLLBACK, SAVEPOINT, SET TRANSACTION

Each of these sublanguages serves a distinct function, enabling comprehensive control over database management and data manipulation.