Edit
Solution mentioned by @leftclickben is also effective.
We can also use a stored procedure for the same.
CREATE PROCEDURE get_tree(IN id int)
BEGIN
DECLARE child_id int;
DECLARE prev_id int;
SET prev_id = id;
SET child_id=0;
SELECT col3 into child_id
FROM table1 WHERE col1=id ;
create TEMPORARY table IF NOT EXISTS temp_table as (select * from table1 where 1=0);
truncate table temp_table;
WHILE child_id <> 0 DO
insert into temp_table select * from table1 WHERE col1=prev_id;
SET prev_id = child_id;
SET child_id=0;
SELECT col3 into child_id
FROM TABLE1 WHERE col1=prev_id;
END WHILE;
select * from temp_table;
END //
We are using temp table to store results of the output and as the temp tables are session based we wont there will be not be any issue regarding output data being incorrect.
Try this query:
SELECT
col1, col2, @pv := col3 as 'col3'
FROM
table1
JOIN
(SELECT @pv := 1) tmp
WHERE
col1 = @pv
SQL FIDDLE Demo
:
| COL1 | COL2 | COL3 |
+------+------+------+
| 1 | a | 5 |
| 5 | d | 3 |
| 3 | k | 7 |
Note
parent_id
value should be less than thechild_id
for this solution to work.