1. A computer-implemented method of performing an electronic database search, the method comprising: receiving a request to identify database records that satisfy a specified condition, the records being of a type that has, for a property, a defined validity range bounded by a value for a first attribute and a value for a second attribute, wherein the specified condition is of a type that is satisfied for a record when for a record both a first inequality condition on the first attribute value and a second inequality condition on the second attribute value are satisfied; and executing a scan of an index for the database records, the index including, for each of the records, the first attribute value for the record and an encoded value of the second attribute value for the record, the encoded value being one of multiple unique digital values for each of multiple consecutive ranges for the property within which the second attribute falls, the scan identifying records for which both the inequality condition on the first attribute value and an equality condition on the encoded value for the second attribute value are satisfied.