A Query Language for Statistical Databases

In this chapter we describe a high level, screen-oriented database query language, Summary-Table-by-Example (STBE) for manipulating summary data in statistical databases. STBE uses aggregate functions, relations with set-valued attributes and surrmary tables to extract and format summary data in tabular form. STBE is similar to Query-by- Example, and is a superset of another language, Aggregates-by-Example (ABE). Summary tables are shown to be information equivalent to a set of relations. This equivalency allows STBE to convert a summary table referenced in a query into a set of relations and to evaluate the query in a uniform manner. The expressive power of STBE is at least that of the relational calculus that allows set-valued attributes and aggregate functions. STBE is compared with ABE and SQL. Access path selection in STBE is discussed briefly.