Range Query

Synonyms

Range search; Range selection

Definition

Consider a relation R with some numeric attribute A taking values over an (ordered) domain D. A range query retrieves all tuples in R whose attribute A has values in the interval [low, high]. That is, low ≤ R.A ≤ high. The range interval may be closed as above, open (e.g., low < R.A < high), or half-open in either side (e.g., low < R.A ≤ high). A range query can be one-sided (e.g., low ≤ R.A retrieves all tuples with R.A value greater or equal to low). When low = high the range query becomes an equality (or membership) query.

Key Points

Range queries involve numeric (or numerical) attributes. These are attributes whose domain is totally ordered and thus a query interval (e.g., [low, high]) can be formed. In contrast, attributes whose domain is not naturally ordered are called categorical (or nominal). Range queries correspond to selections and are thus amenable to indexing. The standard access method for a range query on some attribute A...