-- Data Definition Language (DDL)

-- Subset of SQL used to define and manage the structure of a database (Schmeas, tables, indexes)

-- Examples 
-- CREATE - Create a new table or database 
-- ALTER - Modify the structure of an existing table 
-- DROP - Delete a table or database 

-- Purpose: Deals with schema-level changes, not the actual data inside the tables 


-- Data Manipulation Langauge (DML)
-- Subset of SQL used to maniuplate the data stored in the database 

-- Examples 
-- SELECT - Retrieve Data 
-- INSERT - Add new Data 
-- UPDATE - modify existing data 
-- DELETE - Remove Data 

-- Purpose it deals with row-level operations, changing or querying the actual data. 

-- KEY DIFFERENCE 
-- DDL - Defines Structure (Tables, Columns, constraints)
-- DML - Manipulates data (Rows inside the table)


-- FOREIGN KEY - in the child table references a primary key or unique key in the parent table to maintain referential integrity 
-- Ensures that every foreign key value corresponds to an existing record in the parent table 


-- Data Control Language (DCL) - it is a sublanguage of SQL used to manage access and permissions in a database. 
-- Commands control who can do what on database objects. 

-- GRANT -- Gives a user specific prvileges on a Database object 
-- REVOKE -- Removes previously granted privileges

-- Purpose - Ensures security and controlled access to data, works alongside authentication and roles. 

-- Referential Integrity - is a concept in relational databases that ensures the relationships between tables remain consistent 

-- Means that a foregin key in one table must either: 
-- match a primary key value in another table or be NULL (if allowed)
-- Prevents orphaned records and maintains valid links between related data.