SelectWithUnionQuery (children 1)
 ExpressionList (children 1)
  SelectQuery (children 2)
   ExpressionList (children 1)
    Literal \'string\' (alias str)
   ExpressionList (children 1)
    Function concat (children 1)
     ExpressionList (children 2)
      Identifier str
      Literal \'_abc\'