SelectWithUnionQuery (children 1)
 ExpressionList (children 1)
  SelectQuery (children 1)
   ExpressionList (children 1)
    Function avg (children 1)
     ExpressionList (children 1)
      Function arrayJoin (children 1)
       ExpressionList (children 1)
        Literal Array_[NULL, UInt64_1, UInt64_2]
