SQL Server provides a basic set of aggregation functions, such as MIN, MAX, and SUM. However, when you need other aggregations, you need to develop your own custom solutions. For example, you might need a custom aggregation solution for string concatenation to generate, say, an itinerary of flights all in one string. Or, you might need other aggregation solutions such as aggregate product (to calculate compound interest rates, for example), aggregate median (for statistical analysis), or aggregate bitwise operations (to calculate effective user permissions, for instance).

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