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General

View Vs Materialized View

Difference Between View and Materialized View

View

A view is a virtual relation, which performs as an actual relation without being a part of a logical relational model in the database system. The view is a virtual table created by using command Create View. In Create View Command, a virtual table consist of the data retrieved from query expression.

The result of creating views is never stored anywhere in the disk and every time the user needs to raise a query whenever data is required. So as an outcome, we get updated or latest data from original tables. As mentioned, View is not stored on the disk; instead, it is computed each time when it is accessed or used.

The overall performance of view depends on the selected query and in case if we want to improve the overall performance of view, we need to avoid using join statements within our query, or we need to use multiple joins between tables. To have numerous joins between meals, you need to use an index-based column, as index-based columns are faster in performance than non-index based columns.

To update any content in View, you need to make changes in the original base table, which is reflected directly in its view and therefore, this makes its performance slower. The user can easily create a customized look of a complex database, in which the user can restrict other users from accessing the sensitive information or data stored in a database. This also results in a reduction of the overall complexity of queries by retrieving data from several tables in a single customized View.

Syntax of View:

Create View A AS <Query Expression>

Advantages of Views

  • Views can directly represent a subset of data contained within a database or table, and it can also limit its degree of exposure for underlying tables to the outer world.
  • Views can easily simplify and join multiples tables in one virtual table
  • Aspects can also be treated as aggregate tables in which the database engine will aggregate the overall data and provide the calculated result as the part of data
  • Pictures can completely hide the complexity of data

Materialized View

An appeared view is a physical copy of the original base tables like a snapshot or image of the unique base table. Materialized View also contains the data that are retrieved from Query Expression of command. Create Materialized View.

Materialized View is stored on a disk and precomputed like an object, and it does not get updated each time when it is accessed. It requires manually updating in case of saving the changes with the help of triggers. called Materialized View Maintenance.

On comparison, the materialized view responds faster than light because the materialized view is pre-computed and stored on disk. So, it does not require any extra time in resolving queries each time. This results in the Materialized View responses faster than standard View.

Materialized View is more useful in saving time-required for computation by accessing it frequently. Materialized View is mostly used in Data Warehouse. There are mainly three ways for updating Materialized View, which is as follows:

  • Materialized View is updated as soon as its relation is defined
  • Materialized View can be updated each time when it is accessed
  • Materialized View is periodically updated

Advantages of Materialized Views

  • Materialized Views can quickly improve the overall performance of queries, which uses the same sub-query results every time.
  • Materialized Views are transparent and automatically maintained with the help of Snowflake, which is a background service and gives background updation after every change within the database of materialized views. This causes a low chance of any errors, and efficient outcome is obtained compared to manual updating of Materialized Views.
  • The data accessed in the database through Materialized Views are also current, regardless of the number of times changes are made within the database system. In case of any query is raised, Snowflake retrieves the newer data and updates it automatically.

Critical differences between View and Materialized View

  • One of the fundamental is that Views are not physically stored on the disk and so, each time it gets updated when accessed while on the other hand, Materialized Views are directly stored on the disc.
  • The view is determined as a Virtual table created as an outcome of Query Expression while Materialized View is established as a physical copy, which can be in picture or snapshot format of the base table.
  • Views need to be updated each time about which View is defined, as the tuples of views are computed while in case of Materialized Views, it is updated as soon as the tuples are stored in a database. Depending on the database, Materialized View can be updated in three ways.
  • Another dissimilarity between View and Materialized View is that, when we create a view using the virtual table, row id of View is utterly similar to the original table while in case of Materialized View, when it is created, row id of Materialized View is entirely different.
  • In the case of View, whenever the user accesses it, updated data is observed while in the case of Materialized View, the user needs to refresh every time after obtaining it to get the updated database.
  • The overall performance of View is slower than Materialized View because View is not stored in the disk while materialized view is stored on the disk, which helps the user to access the last updated database easily and therefore, results in high performance.
  • On creating a view, it provides only logical View of the table, and no separate copy of the table is created while on the other hand, when Materialized View is created, it provides a complete physical separate copy of the table.
  • One last difference between View and Materialized View is that View is updated automatically whenever it is accessed while Materialized View is updated with an extra trigger or some automatic process is applied to update the data stored in a database.

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  3. Decode in SQL
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