Q. When should I consider implementing OLAP Services?
A. Basically, any business process that requires you t analyze (roll up, drill down, and so on) transactional data across a variety of categories is an excellent application of OLAP technology. Loosely speaking, any time you have created an Excel pivot table, you have started to explore the OLAP technology.
Q. What is the difference between relational and multidimensional databases?
A. The primary difference between a relational database and a multidimensional database is semantics. The true differentiation is the manner in which data is represented, and not the underlying technology. Relational databases tend to represent data in a flat, two dimensional manner, whereas multidimensional databases have the capability to reprsent data across many dimensions.
It is important to note that the underlying technology between the two kinds of databases does not have to be different. It is possible to create a multidimensional database using SQL Server 7.0. This is a complex task, requiring sophisticated database schemas, such as star schemas, but it can be done. Likewise, it would be possible to create a standard two-dimensional relational database using OLAP Services by creating cubes with only two dimensions.
Q. How do I translate my transactional data into an effective multidimensional database?
A. In OLAP Services, the multidimensional database is based in a data source; typically this data source is the database that holds your transactional data. In order to create the multidimensional database, you must translate your data. Translating this relational data into an effective multidimensional database requires careful thought and a true understanding of the base data and how your users need to analyze data.
Basically, the translation involves choosing the appropriate tables and columns within those tables to represent the dimensions and measures of your cube. As is the case with most thing, this is often easier said than done. The trick to effectively translating your data is to truly understand the underlying data. In most cases, it is necessary to have many people involved in designing the cubes that make up the multidimensional database.
Q. Can I analyze data that is calculated from my source data such as net profit?
A. Yes, OLAP Services supports calculated members. A calculated member is essentially a measure that does not have a value explicitly stored in the underlying fact table but whose value can be derived from other values that are explicitly stored in the fact table. Once you have defined a calculated member, it appears as any other measure within the cube and its source is invisible to the user.
This FAQ is taken from "Microsoft SQL Server 7.0 DBA Survival Guide" by SAMS.
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By 6 Users
12/6/2001 9:46:34 PM: 
