public virtual ExceptExpression Update(SelectExpression source1, SelectExpression source2) => source1 != Source1 || source2 != Source2 ? new ExceptExpression(Alias, source1, source2, IsDistinct) : this;
public ExceptExpression(string alias, SelectExpression source1, SelectExpression source2, bool distinct) : base(alias, source1, source2, distinct) { }