SelectWithUnionQuery (children 1)
 ExpressionList (children 1)
  SelectQuery (children 2)
   ExpressionList (children 2)
    Function equals (children 1)
     ExpressionList (children 2)
      Identifier table2.parent_id
      Literal \'\'
    Function isNull (children 1)
     ExpressionList (children 1)
      Identifier table2.parent_id
   TablesInSelectQuery (children 2)
    TablesInSelectQueryElement (children 1)
     TableExpression (children 1)
      TableIdentifier table1
    TablesInSelectQueryElement (children 2)
     TableExpression (children 1)
      TableIdentifier table2
     TableJoin (children 1)
      Function equals (children 1)
       ExpressionList (children 2)
        Identifier table1.id
        Identifier table2.parent_id