If you're going to use an OLAP server to develop an analysis application, you must learn the server's query language—in the case of Analysis Services, MDX. And to write efficient, accurate queries, you have to understand how that language treats nulls (empty data cells). The treatment of empties usually varies between OLAP servers. Even though two OLAP servers (e.g., Analysis Services and Hyperion's Essbase) might both support MDX as their query language, they don't necessarily treat empties the same way.

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