SelectWithUnionQuery (children 1)
 ExpressionList (children 1)
  SelectQuery (children 1)
   ExpressionList (children 2)
    Function toFixedString (alias a) (children 1)
     ExpressionList (children 2)
      Literal \'aa\'
      Literal UInt64_2
    Function concat (children 1)
     ExpressionList (children 2)
      Identifier a
      Identifier a