SelectWithUnionQuery (children 1)
 ExpressionList (children 1)
  SelectQuery (children 2)
   ExpressionList (children 2)
    Literal \'a\' (alias key)
    Literal \'b\' (alias value)
   ExpressionList (children 1)
    Function ignore (children 1)
     ExpressionList (children 1)
      Literal UInt64_1
