Methods for gap detection in a temporally unique index in a relational database. A temporally unique index is provided in a relational database. The index includes a first set of keys, each including one or more non-temporal and two temporal key parts. In response to receiving an insert, update, or delete statement for a changed row, the rows with identical non-temporal key parts to the changed row are identified. The temporal key parts of the identified rows are compared to the temporal key parts of the changed row to determine whether: the changed row is directly adjacent to a temporally earlier row and temporally later row, a gap is detected between the changed row and a temporally earlier row, or a gap is detected between the changed row and a temporally later row.