Inherent Complexity of Data Warehouse Databases
Data Warehouse Databases are Large
Since data warehouse databases are constructed by combining selected data from several operational databases, data warehouse databases are inherently large. They are often the largest databases within an organization. The very size of these databases can make them very difficult and expensive to query.
Because data warehouse databases are constructed by combining data from several operational databases, data warehouse databases are structurally complex. They have many tables with a variety of relationships existing between the tables. This complexity makes them particularly difficult to query, because a typical question will involve a number of tables and each table must be properly joined into the logic of the query. Most business users have difficulty even knowing which tables must be included, much less how they must be joined into a question.
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