VIEWS

• Views in SQL are kind of virtual tables. 
• A view also has rows and columns as they are in a real table in the database. 
• We can create a view by selecting fields from one or more tables present in the database. 
• A View can either have all the rows of a table or specific rows based on certain condition.
• Simplify the complex SQL queries.
• Provide restriction to users from accessing sensitive data.

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Syntax:

CREATE VIEW view_name AS 

SELECT column1, column2 FROM table_name WHERE condition;

CREATE VIEW emp_view AS

SELECT emp_id, emp_name, salary

FROM employees

WHERE salary > 50000;

This creates a view named emp_view that only shows employees with salary > 50,000.

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Why

Benefit	Explanation

✅ Simplify complex queries

Write once, use many times

✅ Enhance security

Hide sensitive columns (e.g., passwords)

✅ Logical abstraction

Treat query results as a table

✅ Data consistency

Centralize business logic

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Limitations of Views

• Views do not store data — underlying tables must exist.

• Some views are not updatable (e.g., views using GROUP BY, JOIN, or DISTINCT).

• Performance may be impacted if nested queries are complex.

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Types of Views

·       Simple View: A view based on only a single table, which doesn't contain GROUP BY clause and any functions.

·       Complex View: A view based on multiple tables, which contain GROUP BY clause and functions.

·       Inline View: A view based on a subquery in FROM Clause, that subquery creates a temporary table and simplifies the complex query.

·       Materialized View: A view that stores the definition as well as data. It creates replicas of data by storing it physically.

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