{                        }
    { { MAX     }            }
    { { MIN     }            }
    { { TOTAL   } value-expr } OF rse
    { { AVERAGE }            }
    {                        }
    { COUNT                  }
    {                        }

    Specifies a value by forming a record stream (as indicated
    by a record selection expression), and evaluating its value
    expression against every record in the record stream. Statistical
    expressions are sometimes called aggregate expressions because
    they calculate a single value for a collection of records. When
    you use a statistical expression (except for COUNT), you specify
    a value expression and an RSE. A layered product evaluates the
    value expression for each record in the record stream formed by
    the RSE. Then the product calculates a single value based on the
    results of the first step.

    The COUNT expression differs from the other statistical operators
    because it operates on the record stream defined by the RSE,
    rather than on values in that record stream. It returns the
    number of records in the record stream. In the following
    expression, the number of employees working in New Hampshire
    is returned.

    COUNT OF E IN EMPLOYEES WITH STATE IN E = "NH"