Databases Reference
In-Depth Information
The Aggr function
The output of the
Aggr
function can be likened to the list of values a straight
table would display when evaluating an expression over a certain dimension.
For instance, the following straight table has the
Flight Type
field as the dimension
and
Sum([# Departures Performed])
as the expression.
Essentially, the
Aggr
function creates a virtual straight table, similar to the earlier
one, so that we can further process the list of values that would appear in the
expression column, without even creating the actual object. The result of the
Aggr
function can be used to:
• Create a calculated dimension and perform a nested aggregation
• Perform additional aggregations based on the resulting set of values
Let's see examples for both of these.
Using Aggr for nested aggregation
Since HighCloud Airlines' users are interested in discovering key players in the
industry from different perspectives, they now require a visualization object that
clearly identifies carrier coverage of interstate routes.
To know how many interstate routes each carrier covers, we would simply create a
chart similar to the following screenshot:
