A database view defines table joins for reporting purposes:
For example, a Database View can join the Incident table to the Metric Definition and Metric Instance tables. This view can be used to report on incident metrics and may include fields from any of these three tables.
Several useful Database Views are installed with the Database View plugin and the Database Views for Service Management plugin. These Database Views cover most metric reporting needs and greatly reduce the need to define new ones.
Any user who can create a report can use Database Views as the report source, but ACLs on the underlying tables are honoured.
Note:
The accumulated impact on performance grows as the number of tables that are included in the view and the number of records that those tables contain increase. To maximize the performance of the database view, ensure that the ‘where’ clauses that are defined in the database view are based on indexed fields.
A database view is not treated like a custom table, so there is no licensing impact.
Database view tables are not included in FTP exports.
Database Views cannot be created on tables that participate in table rotation.
It is not possible to edit data in the Database View output.
Database View tables cannot be added as a data preserver in clone requests
In simple words, Database View looks like a table, but it is not a table itself. It is just a visible presentation of tables mapped fields for reporting needs. The view of mapped fields is not stored, so it is impossible to export them.