Working of Database

Databases are systems designed to store, organize, and manage data efficiently, enabling users and applications to retrieve, update, and analyze information.

Query Processing

When a user submits a query (e.g., SELECT * FROM Users WHERE age > 30), the DBMS:

1. Parses & Validates: Checks syntax and table/column existence.
2. Optimizes: Generates the most efficient execution plan (e.g., choosing indexes or join order).
3. Executes:
   1. Reads data from disk/memory.
   2. Applies filters, joins, and aggregations.
   3. Returns results to the user.

Example Query Workflow:

SELECT name FROM Users WHERE country = 'USA' ORDER BY name;  

• Steps:
  • Scan the Users table.
  • Filter rows where country = ‘USA’.
  • Sort results by name.
  • Return the name column.