Sintáxis:
CREATE AGGREGATE agg_name [AS] (BASETYPE = data_type, [SFUNC1 = sfunc_1, STYPE1 = sfunc1_return_type] [SFUNC2 = sfunc_2, STYPE2 = sfunc2_return_type] [,FINALFUNC = final-function] [,INITCOND1 = initial-cond1][,INITCOND2 = initial-cond2]);