Hi,
Derived Table:
Derived tables are tables that you define in the universe schema. You create objects on them as you do with any other table. A derived table is defined by an SQL query at the universe level that can be used as a logical table in Designer.
Derived tables have the following advantages:
u2022 Reduced amout of data returned to the document for analysis. You can include complex calculations and functions in a derived table. These operations are performed before the result set is returned to a document, which saves time and reduces the need for complex analysis of large amounts of data at the report level.
u2022 Reduced maintenance of database summary tables. Derived tables can, in some cases, replace statistical tables that hold results for complex calculations that are incorporated into the universe using aggregate awareness. These aggregrate tables are costly to maintain and refresh frequently. Derived tables can return the same data and provide real time data analysis. Derived tables are similar to database views, with the advantage that the SQL for a derived table can include BusinessObjects prompts.
Disadvantages:
Derived tables decrease the readability of the query and must be repeated for each use in a statement. Also, the derived tablemake a query more difficult to read and thus to maintain.
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