Question

Using MySQL, I want to return a list of parents, from a table that has a field structure like this. ID,PARENTID,NAME (a standard parent-child hierarchy). I would like to traverse “up” the tree to return a list of ALL ‘parents’.

I realize that “nested set”, might be a better way to handle this – but currently I cannot change the structure of the data. I will look to do that in the future. Currently – my set of data will realistically contain a few levels of depth – nothing crazy… maybe 2-5 so my recursive hit shouldn’t be ‘too expensive’.

I’ve looked at the solutions presented in SQL Server get parent list – but this syntax bombs in mySQL…

Does anyone have an example of how to do this?

@kevin – thx for link – but I still get error. (“every derived table must have it’s own alias”)

Here’s what I did (modified syntax form above article – to ‘fit’ MySQL) – I clearly missed something…

SELECT parents.*
FROM  (
    SELECT taskID,  task,  parentID,  0 as level
    FROM   tasks
    WHERE taskidID = 9147
    UNION ALL
    SELECT  taskID, task,  parentID,  Level + 1 
    FROM   tasks
    WHERE  taskID = (SELECT parentID FROM parents ORDER BY level DESC LIMIT 1)
    )

thoughts???

EXAMPLE:

ID      PARENTID    NAME
9146    0       thing1
9147    0       thing2
9148    9146        thing3
9149    9148        thing4
9150    0       thing5
9151    9149        thing6

Query for parents of “thing3”
Returns “9148,9146”

Query for parents of “thing6”
Returns “9149,9148,9146,0”

Answer 1

In this example we are checking 5 levels up:

select 
    t1.parentid, t2.parentid, t3.parentid, t4.parentid, t5.parentid
from
    tableName t1
    left join tableName t2 on t1.parentid = t2.id
    left join tableName t3 on t2.parentid = t3.id
    left join tableName t4 on t3.parentid = t4.id
    left join tableName t5 on t4.parentid = t5.id
where
    t1.name = 'thing3'