SelectWithUnionQuery (children 1)
 ExpressionList (children 1)
  SelectQuery (children 1)
   ExpressionList (children 4)
    Subquery (alias x) (children 1)
     SelectWithUnionQuery (children 1)
      ExpressionList (children 1)
       SelectQuery (children 1)
        ExpressionList (children 2)
         Function toDate (children 1)
          ExpressionList (children 1)
           Literal \'2015-01-02\'
         Literal \'Hello\'
    Identifier x
    Function identity (children 1)
     ExpressionList (children 1)
      Subquery (children 1)
       SelectWithUnionQuery (children 1)
        ExpressionList (children 1)
         SelectQuery (children 1)
          ExpressionList (children 1)
           Literal UInt64_1
    Function identity (children 1)
     ExpressionList (children 1)
      Subquery (alias y) (children 1)
       SelectWithUnionQuery (children 1)
        ExpressionList (children 1)
         SelectQuery (children 1)
          ExpressionList (children 1)
           Literal UInt64_1