The main component of a database is its table. The data in a table may be useful to different people for different purposes, which may also be compulsory to protect from various factors.
The concept of View exists for making data accessibility custom or restricting access to data.
Key Takeaways
- A view is a virtual table that displays the result of a query, while a materialized view is a physical copy of the data resulting from a query.
- Materialized views store data and must be refreshed periodically, whereas views retrieve data from the underlying tables in real time.
- Materialized views improve query performance by storing precomputed data, while views may require additional processing time as they access data from base tables.
View vs Materialized View
A view in a database is a virtual table based on the result-set of a SQL statement, while a materialized view is a physical copy of the data resulting from a query that is stored in the database.
Views are the logical virtual tables that are created with the help of a ‘select query.’ And its results are not stored. It is only displayed.
Also, the View is updated every time it is accessed or used. Customized tables can also be made. But it has a slow processing speed.
Materialized views are also the logical virtual tables that are created by the ‘select query.’ But these are stored on a disk. They are not updated every time they are accessed.
Their update takes place manually as well as with the help of triggers. It has a fast processing speed.
Comparison Table
| Parameters of Comparison | View | Materialized View |
|---|---|---|
| Meaning | A virtual table is formed from single or multiple base tables or views. | It is a base table’s photocopy or snapshot. |
| Storage | It is only displayed and not stored. | It is always stored on the disk. |
| Update | Every time it is utilized, the view is updated. | The update takes place manually as well as with the help of triggers. |
| Processing | It has a slow processing speed. | It has a fast processing speed. |
| Memory Space | Here there is no requirement for memory space. | Here there is a requirement for memory space. |
| Syntax | Its syntax is as follows: Create View V As. | Its syntax is as follows: Create Materialized View V Build [clause] Refresh [clause] On [Trigger] As. |
What is View?
Usage of the ‘Create View’ command can help create a virtual table. This table is called View. The virtual table that is created has certain data. This is recovered from the query expression in the ‘Create View’ command.
A view can be created by using not only one but multiple base tables or views. These can be queried in a similar way to the original base tables.
It is not previously computed and then stored on a disk. It is computed every time it is accessed or used. The execution of expression takes place whenever it is used.
Therefore, a view always has an updated version of the data. Whenever a certain content is updated in View, it also gets updated in the original base table.
Similarly, whenever certain content is updated in the original base table, it is also updated in the View.
However, it affects the View’s performance by making it slower. This view has many advantages. The biggest one of them is not requiring any memory space to store the data.
A customized view of complex databases can also be created as per one’s preference. Restrictions can be applied to protect sensitive information in a database.
What is Materialized View?
The original base table’s photocopy, which is saved, is the materialized View. In simple terms, it is a version that seems to be a photo or snap of the base tables.
It is also filled with certain data, and this too is which was recovered from the ‘Create Materialized View’ command’s query expression.
However, a materialized view is previously computed and must be stored on a disk. Whenever any data is changed in the original base tables, it is not updated here in the materialized View.
Similarly, the original base table is not updated whenever any data is changed in the materialized view. Therefore it is not automatically updated.
The update needs to be done manually. The updates can also be done with the help of triggers. Materialized View Maintenance is the terminology for updating the Materialized View.
Materialized View also has many advantages. Here the biggest advantage is that it responds faster in comparison with View. This is due to the fact that the data is previously computed. This is why no time is wasted on resolving the query.
Therefore responses are faster to the query made on a materialized view. The syntax for the materialized view is as follows: Create Materialized View V; Build [clause] Refresh [ type]; ON [trigger ]; As <query expression>.
Main Differences Between View and Materialized View
- Usage of the ‘Create View’ command can help create a virtual table. This table is called View. The original base table’s photocopy, which is saved, is the materialized View.
- The view is only displayed and not stored. Materialized View is always stored.
- In the case of View, every time it is utilized, the View is updated. In the case of materialized View, the update takes place manually as well as with the help of triggers.
- The view has a slow processing speed. Materialized View has a fast processing speed.
- In the case of View, there is no requirement for memory space. In the case of materialized View, it is a requirement of memory space.
- View’s syntax is as follows: Create View V As. Materialized view’s syntax is as follows: Create Materialized View V Build [c] Refresh [c] On [t] As. c- clause; t- trigger
- http://128.148.32.110/courses/cs227/archives/2008/Papers/MaterializedViews/Paraboschi.pdf
- https://dl.acm.org/doi/abs/10.1145/375663.375703
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