Full Form of DDL
DDL stands for Data Definition Language. It is a subset of SQL (Structured Query Language) used to define and manage all the data structures in a database.
Key Components of DDL:
CREATE: Used to create new database objects such as tables, views, and indexes.
ALTER: Allows for modifications to existing database objects, such as adding or deleting columns in a table.
DROP: Used to delete database objects like tables or views from the database permanently.
TRUNCATE: Removes all records from a table without logging individual row deletions, while keeping the table structure intact.
Importance of DDL:
Database Structure: DDL helps in establishing the structure of the database by defining tables, fields, and relationships.
Data Integrity: By defining constraints like primary keys, foreign keys, and unique constraints, DDL ensures the integrity of the data.
Schema Management: DDL commands allow for easy management and modification of the database schema as requirements evolve.
Examples of DDL Commands:
Creating a Table:
sql
CREATE TABLE Employees (
ID INT PRIMARY KEY,
Name VARCHAR(100),
Age INT
);Altering a Table:
sql
ALTER TABLE Employees ADD COLUMN Salary DECIMAL(10, 2);Dropping a Table:
sql
DROP TABLE Employees;
Understanding DDL is essential for anyone working with databases, as it lays the foundation for how data is organized and accessed.