Databases Reference
In-Depth Information
Drill-Through
Drill down is the process of navigating from a summary level to more detailed
levels across a cube dimension. Drill-through is a completely different animal.
Drill-through retrieves fact data corresponding to a cell or some specified
range of cells. Often the lowest level of detail in a cube is still comprised of ag-
gregated values, but users occasionally have a need to see the associated
row-level data from the fact table. In Analysis Services 2005, even if you use
the MOLAP storage mode (discussed later in this chapter), you can still use
drill-through. You can modify a server configuration advanced property,
OLAP\Query\DefaultDrillthroughMaxRows, control the default size of the re-
turned dataset.
By default, drill-through returns the granularity attribute of each dimension and
all measures. If you want your drill-through action to behave like drill-through in
Analysis Services 2000, you can create a ROLAP dimension from the fact
table that contains the measures to return. And just how do you define drill-
through? You could create an application that performs drill-through program-
matically using the SQL query supported by Analysis Services 2005. A new
option in Analysis Services 2005 is to create a drill-through action. The follow-
ing sections describe the available action types, including how to create a drill-
through action.
For some insight on how drill-through actually works in Analysis Services
2005, it is informative to contrast it to the implementation of drill-through in
Analysis Services 2000. Analysis Services 2000 fetched all requested meas-
ures directly from the relational data source which is potentially a slow pro-
cess. Analysis Services 2005 fetches the requested measures from the
MOLAP database directly and therefore runs much faster. Indeed, the system
is self-contained and requires no connection to SQL Server. Drill through can
be defined as an Action (to be seen in next section) and can drill through on
cells that have drill through action defined. You will learn to define Drill through
and understand it's behavior in the next section.
Actions
Actions are predefined metadata components stored on the server that send
commands to client applications to perform certain operations based on a se-
lection by the user in the cube browser. For example, the user could select di-
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