PostgreSQL – How to Create a Materialized View

Creating a materialized view in PostgreSQL involves using the CREATE MATERIALIZED VIEW statement. A materialized view is a precomputed and stored view of the data from one or more tables. Using materialized views can improve query performance by reducing the need to repeatedly compute the same complex queries. Here’s the basic syntax for creating a materialized view:

CREATE MATERIALIZED VIEW view_name AS SELECT columns FROM source_tables [WHERE conditions] [GROUP BY columns] [ORDER BY columns] [WITH [NO] DATA];

where

• view_name is the name you want to give to the materialized view.
• columns are the columns you want in the materialized view, derived from the SELECT statement.
• source_tables are the name of the source table(s) or views and any necessary JOIN clauses to retrieve the data you want to store in the materialized view.
• conditions (optional): You can specify conditions to filter the data from the source tables.
• GROUP BY columns (optional): If you want to group the data by specific columns, you can use the GROUP BY clause.
• ORDER BY columns (optional): You can specify an order for the data in the materialized view using the ORDER BY clause.
• WITH [NO] DATA: This option specifies whether you want to populate the materialized view with data immediately (WITH DATA) or create the view without data (WITH NO DATA). You can later refresh the view with data using the REFRESH MATERIALIZED VIEW command.

Here’s an example of creating a materialized view that stores the total sales amount for each product in a sales database:

CREATE MATERIALIZED VIEW total_sales_by_product AS 
SELECT product_id, SUM(sale_amount) AS total_sales 
FROM sales 
GROUP BY product_id;

In this example, total_sales_by_product is the name of the materialized view, and it calculates the total sales amount for each product based on the sales table.

After creating the materialized view, you can query it like a regular table. Keep in mind that materialized views need to be refreshed periodically to update their data. You can use the REFRESH MATERIALIZED VIEW command to update the data in a materialized view:

REFRESH MATERIALIZED VIEW view_name;

You can schedule regular refreshes using cron jobs, database triggers, or other mechanisms based on your specific requirements.