Views are virtual tables based on the result set of a SQL statement. Think of them as stored queries that can be treated as if they were tables. When you access a view, PostgreSQL runs the underlying query and presents the results.

Key Features

  1. Abstraction: Views hide query complexity from end users
  2. Security: Control access to sensitive data by exposing only specific columns/rows
  3. Data Independence: Changes to underlying tables don't affect applications using views
  4. Query Reusability: Complex queries can be saved and reused easily

Types of Views

Views

1. Standard Views

  • Virtual tables that run their query each time they're accessed
  • Always show current data
  • No additional storage required
  • Ideal for frequently changing data

2. Materialized Views

  • Store the result set physically
  • Must be refreshed to see updated data
  • Excellent for complex queries with infrequently changing data
  • Improve query performance for expensive computations

Example 

CREATE VIEW product_level_sales_of_top_regions AS
WITH regional_sales AS (
    SELECT
        region,
        SUM(amount) AS total_sales
    FROM
        orders
    GROUP BY
        region
),
top_regions AS (
    SELECT
        region,
        total_sales
    FROM
        regional_sales
    WHERE
        total_sales > 10000
    ORDER BY
        total_sales desc
    LIMIT
        10
), prodcut_wise_data as (
    SELECT
        o.region,
        o.product_id,
        SUM(o.qty) AS product_units,
        SUM(o.amount) AS product_sales
    FROM
        orders o
    JOIN
        top_regions tr on tr.region=o.region
    GROUP BY
        o.region,
        o.product_id
)
select
    *
from
    prodcut_wise_data
;
SELECT * FROM product_level_sales_of_top_regions;

Notice how the view:

  1. Simplifies complex queries by presenting them as tables
  2. Provides a way to reuse complex queries
  3. Allows for data masking and security by exposing only specific columns/rows

Best Practices

1. Naming Conventions

  • Use clear, descriptive names
  • Consider prefixing views (e.g., v_active_customers or suffixing with _view)
  • Document the view's purpose

2. Performance Considerations

  • Use materialized views for compute-intensive queries
  • Index materialized views when appropriate
  • Be cautious with view chaining (views referencing other views)

3. Security

  • Grant minimum necessary permissions
  • Use views to implement row-level security
  • Consider using views for data masking

References

Next Steps

In the next parts, we will explore the different types of scans and join strategies in PostgreSQL.

Originally published at https://www.adiagr.com