A materialized view is a concrete table that displays information required by a database, allowing end users to retrieve data through SQL queries. The view stores requested information in a permanent table, making re-accessing information faster but potentially out of date.
The materialized view is a database object in which information required by a database is displayed. A database is a collection of information organized in a table format. It allows the end user to retrieve data through queries posed in SQL (Structured Query Language) format. This allows the end user to make database queries for specific types of information, such as a list of employees under the age of 30. This information would be displayed in an accessible way in the materialized view, provided it is a concrete and virtual table that contains the list of results.
When the end user enters a query into the database, the program immediately starts sifting through his records. Compare the information you are looking for with each individual record in the selected tables. So, continuing the previous example, when looking for employees under 30, the database goes to the “Employees” table and, starting at the beginning, looks at each person’s date of birth, comparing it to the current date to get an age . All employees under the age of 30 are moved to the materialized view table. Only then is the final materialized display list “presented” to the end user, providing a complete answer to the requested question.
Unlike a traditional view for a relational database, which stores query information in a temporary table, the materialized view stores the requested information in a real, permanent, concrete table. The information stored in the materialized view is stored in the system memory, allowing the end user to make changes or update the data from time to time. For example, if the same example query – all employees under 30 – is run on day one, it remains in the system as a materialized view from that point on.
The benefit is that re-accessing information is much faster; the information is already stored in the system. The main drawback is that information can become stale or out of date between access times. For example, if the end user accesses the same materialized view again on day 10, things may have changed: someone may have just turned 30. The materialized view version will not take these changes into account until the entire query has been run again.
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