SelectWithUnionQuery (children 1)
 ExpressionList (children 1)
  SelectQuery (children 2)
   ExpressionList (children 2)
    Identifier a
    Function has (children 1)
     ExpressionList (children 2)
      Literal Array_[NULL, NULL]
      Identifier a
   TablesInSelectQuery (children 1)
    TablesInSelectQueryElement (children 1)
     TableExpression (children 1)
      TableIdentifier 00662_has_nullable