Compares two TPgInterval objects.
function Compare(Value: TPgInterval): integer;
Call the Compare method to compare two TPgInterval objects.
If the current object represents an interval that is longer than Value, Compare returns a positive number. If the current object represents an interval that is shorter than Value, Compare returns a negative number. If the current object equals to Value, Compare returns 0.
Internally INTERVAL values are stored as months, days, and seconds. Compare supposes that months value has more priority than days, and days has more priority than seconds.