They sound almost identical, but choosing between a view and a materialized view is a critical decision in data engineering. Depending on your use-case, you have to weigh data freshness against query speed and compute resources to decide exactly which one fits your workflow.
Views (Virtual Table)
A standard view doesn't actually hold any data. It simply stores the SQL query inside the database catalog. When you query a view, the database looks at the underlying tables and runs that stored query on the fly.
- Performance: It is only as fast as the query written inside it. If the underlying query takes 5 minutes to run, the view takes 5 minutes to load.
- Data Freshness: Always 100 % up-to-date. Because it runs live every single time, it perfectly reflects the exact state of the base tables.
- Security & Logic: Views can be used to provide a restricted view of data where users cannot see the entirety of the data underneath. You can hide sensitive columns (like salaries) from certain users while letting them see the rest of the calculated data.
- Cost: Zero storage cost (since it's just text), but it incurs compute costs and processing time every time it's called.
Materialized Views (Physical Table)
Unlike a standard view, a materialized view actually saves the results of the query to the disk and takes up space. It is a physical table created from a query. It's similar to caching, you run it once to freeze the data so you don't have to keep re-processing the upstream workflow.
- Performance: Very fast. Because the data is already computed and sitting on the disk, reading a materialized view is as fast as reading a regular table.
- Data Freshness: It reflects the data at the time of the most recent refresh. If the base tables change, the materialized view won't show those changes until a database administrator (or an automated script) runs a manual or scheduled refresh.
- Cost: It requires physical disk space to store the results, but saves massively on compute costs if the data is queried frequently.
Which one should you choose?
Go with a View if your data is constantly changing, you always need real-time accuracy, or the underlying query is simple enough that it runs quickly anyway.
Opt for a Materialized View if you are building dashboards on top of massive datasets, running complex aggregations (like SUM or COUNT over millions of rows), and your business users can tolerate data that is a day or a few hours old.