ANSI SQL specifies that
If SUM is specified and DT is exact numeric with scale
S, then the data type of the result is exact numeric with
implementation-defined precision and scale S.
If DT is approximate numeric, then the data type of the
result is approximate numeric with implementation-defined
precision not less than the precision of DT.
However, when summing integer types (first operand) with float or double (second operand), Phoenix returns the value with the same data type as the first operand.
Doing a sum with the first operand being a FLOAT or DOUBLE will return a DECIMAL with a fixed scale of 4.
Doing any multiplication or division will also result in a DECIMAL with scale 4.
In all of the cases outlined above, the return data type does not meet the ANSI standard.