7/25/2019 BO Designer Related FAQs
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Derived Tables:How a derived table is useful than a view in data
base? What are the additional features
derived table provides?
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 define
by an !" #uery at the
universe level that can be used as a lo$ical table in
Desi$ner.
Derived tables have the followin$ advanta$es:
%educed amount of data returned to the document for analysis.You
can include comple& calculations and functions in a derived
table. These operations
are performed before the result set is returned to document '
which saves time and
reduces the need for comple& analysis of lar$e amounts of
data at the report level.
%educed maintenance of database summary tables.
Derived tables can ' in some cases' replace statistical tables
that hold results for comple&calculations that are incorporated
into the universe usin$ a$$re$ate awareness. These
a$$re$ate tables are costly to maintain and refresh fre#uently.
Derived tables can return
the same data and provide real time data analysis.
Derived tables are similar to database views' with the advanta$e
that the !" for
a derived table can include (usiness )bjects *rompts.
+iew,Data (ase-:
n databasetheory' a view consists of a stored #ueryaccessible as
a virtual table
composed of the result set of a#uery. /nli0e ordinary tables
,base tables- in a relational
database'a view does not form part of thephysical schema: it is
a dynamic' virtual tablecomputed or collated from datain the
database. 1han$in$ the datain a tablealters the
datashown in subse#uent invocations of the view.
+iews can provide advanta$es over tables:
+iews can represent a subset of the data contained in a
table+iews canjoinand simplify multiple tables into a sin$le
virtual table
+iews can act as a$$re$ated tables' where the database en$ine
a$$re$ates data ,sum'
avera$eetc- and presents the calculated results as part of the
data+iews can hide the comple&ity of data2 for e&le a
view could appear as ales3444 or
ales3445' transparentlypartitionin$the actual underlyin$
table
+iews ta0e very little space to store2 the database contains
only the definition of a view'not a copy of all the data it
presents
Dependin$ on the !"en$ine used' views can provide e&tra
security
+iews can limit the de$ree of e&posure of a table or tables
to the outer world
http://en.wikipedia.org/wiki/Databasehttp://en.wikipedia.org/wiki/Databasehttp://en.wikipedia.org/wiki/Database_theoryhttp://en.wikipedia.org/wiki/Database_queryhttp://en.wikipedia.org/wiki/Table_(database)http://en.wikipedia.org/wiki/Table_(database)http://en.wikipedia.org/wiki/Query_languagehttp://en.wikipedia.org/wiki/Query_languagehttp://en.wikipedia.org/wiki/Relational_databasehttp://en.wikipedia.org/wiki/Relational_databasehttp://en.wikipedia.org/wiki/Relational_databasehttp://en.wikipedia.org/wiki/Database_designhttp://en.wikipedia.org/wiki/Datahttp://en.wikipedia.org/wiki/Databasehttp://en.wikipedia.org/wiki/Datahttp://en.wikipedia.org/wiki/Datahttp://en.wikipedia.org/wiki/Table_(database)http://en.wikipedia.org/wiki/Table_(database)http://en.wikipedia.org/wiki/Datahttp://en.wikipedia.org/wiki/Join_(SQL)http://en.wikipedia.org/wiki/Join_(SQL)http://en.wikipedia.org/wiki/Join_(SQL)http://en.wikipedia.org/wiki/Sumhttp://en.wikipedia.org/wiki/Averagehttp://en.wikipedia.org/wiki/Averagehttp://en.wikipedia.org/wiki/Partition_(database)http://en.wikipedia.org/wiki/SQLhttp://en.wikipedia.org/wiki/Databasehttp://en.wikipedia.org/wiki/Database_theoryhttp://en.wikipedia.org/wiki/Database_queryhttp://en.wikipedia.org/wiki/Table_(database)http://en.wikipedia.org/wiki/Query_languagehttp://en.wikipedia.org/wiki/Relational_databasehttp://en.wikipedia.org/wiki/Relational_databasehttp://en.wikipedia.org/wiki/Database_designhttp://en.wikipedia.org/wiki/Datahttp://en.wikipedia.org/wiki/Databasehttp://en.wikipedia.org/wiki/Datahttp://en.wikipedia.org/wiki/Table_(database)http://en.wikipedia.org/wiki/Datahttp://en.wikipedia.org/wiki/Join_(SQL)http://en.wikipedia.org/wiki/Sumhttp://en.wikipedia.org/wiki/Averagehttp://en.wikipedia.org/wiki/Partition_(database)http://en.wikipedia.org/wiki/SQL
7/25/2019 BO Designer Related FAQs
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6ust as functions,in pro$rammin$- can provide abstraction' so
database users can create
abstraction by usin$ views. n another parallel with functions'
database users can
manipulate nested views' thus one view can a$$re$ate data from
other views. Without theuse of views the normali7ation of databases
above second normal formwould become
much more difficult. +iews can ma0e it easier to create lossless
join decomposition.
6ust as rows in a base table lac0 any defined orderin$' rows
available throu$h a view donot appear with any default sortin$. A
view is a relational table' and the relational model
defines a table as a set of rows. ince sets are not ordered 8 by
definition 8 the rows in a
view are not ordered' either. Therefore' an )%D9% (Yclause in
the view definition ismeanin$less. The !" standard ,!":344- does
not allow an )%D9% (Y clause in a
subselect in a 1%9AT9 +9W statement' just as it is not allowed
in a 1%9AT9 TA("9
statement. However' sorted data can be obtained from a view' in
the same way as any
other table 8 as part of a #uery statement.;evertheless' some
D(
