SelectWithUnionQuery (children 1)
 ExpressionList (children 1)
  SelectQuery (children 3)
   ExpressionList (children 1)
    Function count (children 1)
     ExpressionList
   TablesInSelectQuery (children 1)
    TablesInSelectQueryElement (children 1)
     TableExpression (children 1)
      TableIdentifier merge_tree
   Function in (children 1)
    ExpressionList (children 2)
     Identifier x
     Literal Tuple_(UInt64_0, UInt64_0)