Using Ado Md to Get Cube Schema Information

Some of the most useful information you can have when starting to work with an OLAP data source is information about the data source itself. How many cubes are on the server? How many dimensions are in each cube? What are the levels available? Answers to these types of questions can help you get acquainted with your OLAP cubes, allowing you to fully understand how the data is organized and structured. These answers can most easily be gained through the use of ADO MD (Microsoft ActiveX Data Objects Multidimensional).

ADO MD allows you to access both data and metadata from an OLAP or multidimensional data provider. Although ADO and ADO MD are related, they have separate object models. Figure 23-9 illustrates the ADO MD object model.

Figure 23-9

Notice that there are two main branches that stem from the Connection object: the Catalog and Cellset branches. The Catalog branch is used to query the metadata or structure of the OLAP data source, and the Cellset branch is used to query the data in the data source.

To get information about the cube schema, you will utilize the Catalog object. You will note that the object hierarchy in the Catalog branch looks very similar to the hierarchy typically found in an OLAP data source. Note how the Catalog/CubeDef/Dimension/Hierarchy/Level/Member structure within the object model can be related to the Database/Cube/Dimension/Hierarchy/Level/Member in an actual OLAP server. This helps when you start thinking about the schema information you need.

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