A View and a Materialized View are database objects that simplify access to data, but they work differently. A View stores only the SQL query, while a Materialized View stores the actual query results. This difference affects storage, performance, and how up-to-date the data is.
In simple terms, a View displays live data every time it is queried, whereas a Materialized View stores a snapshot of the data for faster access.
What Is a View?
A View is a virtual table created from the result of a SQL query. It does not store data itself; instead, it retrieves the latest data from the underlying tables whenever it is accessed.
Characteristics of a View:
- Does not store data.
- Always shows the latest data.
- Requires less storage space.
- May be slower for complex queries.
What Is a Materialized View?
A Materialized View stores the results of a query physically in the database. Since the data is already stored, queries run much faster.
Characteristics of a Materialized View:
- Stores query results.
- Requires additional storage space.
- Offers faster query performance.
- Needs to be refreshed to reflect changes in the underlying tables.
Key Differences
The main differences include:
- Data Storage: A View stores only the SQL query, while a Materialized View stores the query results.
- Performance: Views may take longer to execute complex queries because they retrieve live data each time. Materialized Views provide faster performance since the data is precomputed.
- Data Freshness: Views always display the latest data. Materialized Views show stored data until they are refreshed.
- Storage: Views require very little storage, whereas Materialized Views consume additional disk space.
Common Use Cases
Use a View when:
- You need real-time data.
- Storage space is limited.
- Queries are relatively simple.
Use a Materialized View when:
- Query performance is critical.
- Complex reports are generated frequently.
- Data does not need to be updated instantly.
- Large datasets are analyzed regularly.
Conclusion
Both Views and Materialized Views help simplify data access, but they serve different purposes. A View provides live data without storing it, making it suitable for real-time applications. A Materialized View stores query results for faster performance, making it ideal for reporting, analytics, and complex queries where refreshes can be scheduled as needed.