Views

Explanation

A view is a saved query that behaves like a virtual table. Instead of retyping a complex SELECT everywhere, you store it once with CREATE VIEW and then SELECT from the view by name.

Views are great for:

• Hiding complexity behind a friendly name
• Enforcing a consistent "official" definition of a report
• Restricting columns for security (expose only some columns)

Importantly, a normal view stores no data — it re-runs its underlying query every time you use it.

Syntax

CREATE VIEW view_name AS
SELECT col1, col2
FROM table
WHERE condition;
 
SELECT * FROM view_name;

Interactive Example

Create a view of high earners, then query it. Then create a department-summary view and aggregate over it.

Common Mistakes

• Assuming a view caches data. A regular view recomputes on every use; for heavy queries consider a materialized view or a real table.
• Expecting updates to work. Many views are read-only; don't design writes through them.
• Naming collisions. Give views clear, distinct names so they don't clash with tables.

Best Practices

• Use views to standardize repeated report logic across your team.
• Keep view definitions focused; compose small views into bigger ones.
• Drop and recreate (CREATE OR REPLACE VIEW) when the underlying logic changes.

Practice Question

Create a view called senior_engineers containing employees in department 1 hired before 2020, then SELECT their names ordered by salary.

Summary

A view is a named, reusable query treated like a table. It simplifies complex queries and standardizes reports, but a standard view holds no data and often isn't updatable.

FAQ