Aggregate Functions for Temporal Types

The temporal aggregate functions generalize the traditional aggregate functions. Their semantics is that they compute the value of the function at every instant in the union of the temporal extents of the values to aggregate. In contrast, recall that all other functions manipulating temporal types compute the value of the function at every instant in the intersection of the temporal extents of the arguments.

The temporal aggregate functions are the following ones:

In the examples that follow, we suppose the tables Department and Trip contain the two tuples introduced in the section called “Examples of Temporal Types”.