Microsoft Office Tutorials and References
In Depth Information
Click the MDX Query icon on the toolbar to open the query window and the cube window.
Make sure the appropriate data source is selected at the top.
The cube will display the available Measures and Dimensions, as shown in Figure 1-49 .
Figure 1-49. Running a simple MDX query
In the query window, type the MDX query to retrieve the values from the cube. In this case,
to get the Sum of Sales YTD in the Sales Territory Measure, the query should look like the
one in Figure 1-49 .
Execute and parse the query to view the output in the results window.
Final Pointers for Migrating OLTP Data to OLAP
Now that you know the concepts, let’s see some of the important factors to keep in mind while planning for a
migration. First, you need to be completely aware of why you need to migrate to an OLAP database from an OLTP
database. If you are not clear, it’s a good idea to go back to the section “Online Analytical Processing System” and
make a checklist (and also review the need for a staging section). Be sure to consider the following items:
Make sure that there is no mismatch in column names between the two ends. Most of
the time, you don’t have same columns anyway; in such cases, maintain metadata for the
mapping. ETL tools (in this case, SSIS) support different column names.
While mapping columns between the source and destination, there is a good possibility that
the data types of the columns might not match. You need to ensure that type conversion is
taken care of during transformation.
With OLAP, the idea is to restrict the number of columns and tables and denormalize as much
as possible. So it’s a good idea to remove unwanted columns.
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