Set the summary property Available for Queries to Yes.
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Hierarchies can link items in a business area where no relationship is defined in the database. For more information about business areas, see
Chapter 5, Creating and Maintaining Business Areas
.
What are item hierarchies?
Item hierarchies are relationships between items other than dates. An example of an item hierarchy:
Figure 13–1 Sales item hierarchy
The Sales item hierarchy links a country with its regions, cities and stores. To use this hierarchy a Discoverer end user could use a report that shows sales from a
country perspective. The Discoverer end user could then drill down from country to see sales per region, sales per city or sales per store, and then drill back up to the
country level.
The Sales item hierarchy from a Discoverer end user perspective is shown below.
Figure 13–2 Sales item hierarchy - Discoverer end user perspective
The figure below shows the Sales item hierarchy from a database perspective.
Creating and Maintaining Hierarchies 13-3
Figure 13–3 Sales item hierarchy - database perspective
Note that you do not have to specify that Los Angeles is in the West. You only have to specify that City is under Region in your item hierarchy.
What are date hierarchies?
Date hierarchies are relationships between date items. An example of a date hierarchy:
Figure 13–4 Sales date hierarchy
The Sales date hierarchy links a year with its quarters, months, weeks and days. To use this hierarchy a Discoverer end user could use a report that shows total sales
for each year. The Discoverer end user could then drill down from year to show sales per quarter, sales per month, sales per week and the sales per day, and then drill back
up to sales per year.
A section of the Sales date hierarchy from a Discoverer end user perspective is shown below.
13-4 Oracle Fusion Middleware Administrators Guide for Oracle Business Intelligence Discoverer
Figure 13–5 Sales date hierarchy - Discoverer end user perspective
The figure below shows the Sales date hierarchy from a database perspective.
Figure 13–6 Sample date hierarchy - database perspective
Note:
Each level in the date hierarchy is a calculation based on the Sales_ Orders.SALES_DATE column. The calculations are produced by a date hierarchy
template for more information, see What are date hierarchy templates?
.
What are date hierarchy templates?
Date hierarchy templates enable you to define a date hierarchy that you can apply to date items. A date item uses information that specifies the date, month, year and time.
Discoverer uses this information to calculate for example, quarter, week and days of the week. A date hierarchy template automatically creates items based on a date item,
for example to represent the year or month
You will find it more efficient to reuse a date hierarchy template by applying it to date items rather than redefining the same date hierarchy repeatedly for each date item.
You can use the date hierarchy templates supplied with Discoverer Administrator to define many common date hierarchies, or you can create your own customized date
hierarchies.
Discoverer Administrator includes a default date hierarchy template see the Date hierarchy template figure below that enables you to drill from year to quarter to
month to day:
Creating and Maintaining Hierarchies 13-5
Figure 13–7 Date hierarchy template
About date hierarchies and performance
If you apply a date hierarchy to a date item from an indexed table, a query that includes one of these date items will not use the indexes which can reduce
performance. You can optimize performance in Discoverer Plus by applying date hierarchies to date items from tables that do not rely on indexes.
Example of how a date hierarchy can affect performance in Discoverer Plus
When you load a large fact table that is, a table with many rows that contains a date column for example, transaction_date Discoverer applies the default date hierarchy
to the date item for more information, see Load Wizard: Step 4 dialog
. Discoverer creates a folder containing date items such as Year, Quarter and Month
using the EUL_DATE_TRUNC function for more information, see About truncating
date items and the EUL_DATE_TRUNC function . When a Discoverer end user runs
queries that include these items, any indexes that include the date item in the fact table are not used. Where indexes are not used, performance can be affected.
It is recommended therefore that you do not apply date hierarchies to date items in folders based on fact tables, as fact tables are likely to have indexes.
Example of how performance can be retained
To retain performance you should apply date hierarchies to a separate dimension table.
For example, a transaction_date item in a fact table might join to another dimension table for example, Time Period that specifies time periods. You can load this
dimension table using the Load Wizard and apply date hierarchies to it. You can then create a complex folder containing items from both the dimension and fact tables,
including the items created by the date hierarchy such as Year or Quarter. When a Discoverer end user uses queries that include date hierarchy items Discoverer can use
the date column indexes on the fact table. This can considerably improve performance.
How to create item hierarchies
To create an item hierarchy:
1. Choose Insert | Hierarchy to display the
Hierarchy Wizard: Step 1 dialog .