Get the highest parent id recursively in MySQL I want to find the uppermost parent ID for each entry. For example,
CREATE TABLE t1
(
ID int(11) unsigned NOT NULL,
ParentID int(11) unsigned,
PRIMARY KEY (ID)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE utf8_general_ci;

INSERT INTO t1 (ID,ParentID) VALUES (1,NULL),(2,1),(3,2),(4,3);

I intent to get
ID     Highest ParentID
1      NULL
2      1
3      1
4      1

I planned to create a recursive query (MySQL 8 or MariaDB 10.5) by adding a condition to break the recursive when Parent ID is a specific value (e.g., NULL in the above case). I started with
WITH RECURSIVE cte (ID, ParentID) as (
  SELECT ID,ParentID FROM t1
  UNION ALL
  SELECT t2.ID,t2.ParentID FROM t1 t2
  INNER JOIN cte on t2.ParentID = cte.ID
)
SELECT * FROM cte;

but it does not work as I intend, as it gets the next ParentID instead of recursively.
Sample fiddle.
WITH RECURSIVE 
cte as ( SELECT id, id nextid, parentid 
         FROM t1
       UNION ALL
         SELECT cte.id, t1.id, t1.parentid
         FROM t1
         JOIN cte ON cte.parentid = t1.id )
SELECT Id, nextid RootId
FROM cte
WHERE parentid IS NULL

https://dbfiddle.uk/?rdbms=mysql_8.0&amp;fiddle=209df940143d3e984d418e49929bd847