basics

database is a structured collection of data

In a database, a schema is essentially a blueprint or structure that defines how data is organized. It includes:

🔧 What a Schema Contains:

• Tables (with their columns and data types)

• Relationships between tables (foreign keys)

• Indexes

• Views

• Stored procedures and functions

• Constraints (like primary keys, unique constraints, etc.)

DISTINCT is unique - do not show repeated values

only print Pune, Mumbai, Delhi - not repeat it

GROUP BY CITY

SELECT COLUMN AND MUST GROUP BY SAME COLUMN AND CANNOT SELECT OTHER COLUMN JUST OPERATION ON OTHER COLUMN

DELETE FROM STUDENT; will delete all data

PRIMARY KEY: Unique and not null key

FOREIGHN KEY

CASCADING: Changes in one table also reflect in another table (foreign key)

Alias