SelectWithUnionQuery (children 1)
 ExpressionList (children 1)
  SelectQuery (children 3)
   ExpressionList (children 2)
    Identifier k
    Function avgMerge (children 1)
     ExpressionList (children 1)
      Identifier x
   TablesInSelectQuery (children 1)
    TablesInSelectQueryElement (children 1)
     TableExpression (children 1)
      TableIdentifier summing_merge_tree_aggregate_function
   ExpressionList (children 1)
    Identifier k
