In Reports Builder, data is defined independent of format (layout). Therefore, you should be aware of when to use data links instead of groups.
The layouts of a master/detail report that uses two queries and a data link,
and a group report that uses one query and two groups can be identical. Below
is an example of a default master/detail report and a group report that query
the same data. Notice the difference between the two reports: unlike the group
report, the master/detail report displays department 40. This is because the
data link in the master/detail report causes an outer-join: the link automatically
fetches unrelated data. If you are designing a group report that requires an
outer-join, explicitly add it to your SELECT
statement with (+).
A master/detail/detail report, as shown in the figure below, is a report that contains three groups of data: for each master group, two unrelated detail groups are displayed. To produce a master/detail/detail report or any variation of it, you must use data links. If you try to produce this report with a control break using a single query and three groups the query will establish a relationship between the two detail groups.
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