SelectWithUnionQuery (children 1)
 ExpressionList (children 1)
  SelectQuery (children 4)
   ExpressionList (children 3)
    Literal \'(backward, tail, D)\'
    Identifier id
    Function sequenceNextNode (alias next_node) (children 2)
     ExpressionList (children 4)
      Identifier dt
      Identifier action
      Literal UInt64_1
      Function equals (children 1)
       ExpressionList (children 2)
        Identifier action
        Literal \'D\'
     ExpressionList (children 2)
      Literal \'backward\'
      Literal \'tail\'
   TablesInSelectQuery (children 1)
    TablesInSelectQueryElement (children 1)
     TableExpression (children 1)
      TableIdentifier test_sequenceNextNode_Nullable
   ExpressionList (children 1)
    Identifier id
   ExpressionList (children 1)
    OrderByElement (children 1)
     Identifier id
