A base class for unary functions.
Tells if a value is NULL.
UnaryFunction & operator=(const UnaryFunction &rhs)
IsNull & operator=(const IsNull &rhs)
Expression * clone() const
It creates a new copy of this expression.
This is an abstract class that models a query expression.
TE_DEFINE_VISITABLE IsNull(Expression *arg)
Constructor.
Tells if a value is NULL.