The present disclosure describes methods, systems, and computer program products for using DeltaIterators in a database. One computer-implemented method includes, for each of multiple delta parts of a database that store values of an attribute of a table: identifying, by operation of a computer system, a set of values of the attribute stored in the delta part of the database, and identifying a current value in the set of values; identifying, a first critical value among the multiple current values, wherein the first critical value is a current value of a first set of values of the attribute stored in a first delta part of the database; outputting the first critical value; identifying a next value in first set of values; identifying a second critical value among the next value and the multiple current values except the first critical value; and outputting the second critical value.