cannot use column references in default expression?

[Jignesh Shah <jignesh.shah1980@xxxxxxxxx>]

Could anyone please help me to get rid of following error? I want to set the 'ishuman' column based on the value of 'ID' column but it is not allowing me to do so. Any alternatives?

techdb=> CREATE TABLE Users (
������ ID INTEGER,
������ isHuman������� BOOLEAN NOT NULL
��������������������� DEFAULT (ID IS NULL)
��������������������� CHECK (isHuman = ID IS NULL),
������ Name� VARCHAR NOT NULL);
ERROR:� cannot use column references in default _expression_
techdb=>

Thanks,
Jignesh