mysql to get depth of record, count parent and ancestor records

Posted by Nate on Stack Overflow See other posts from Stack Overflow or by Nate
Published on 2010-05-13T01:58:27Z Indexed on 2010/05/13 2:04 UTC
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mysql

|

query

|

depth

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parent

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count

Hey All,

Say I have a post table containing the fields post_id and parent_post_id. I want to return every record in the post table with a count of the "depth" of the post. By depth, I mean, how many parent and ancestor records exist.

Take this data for example...

post_id   parent_post_id
-------   --------------
1         null
2         1
3         1
4         2
5         4

The data represents this hierarchy...

1
|_ 2
|  |_ 4
|     |_ 5
|_ 3

The result of the query should be...

post_id   depth
-------   -----
1         0
2         1
3         1
4         2
5         3

Thanks in advance!

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