You can use it:
SELECT parent_id, count( * )
WHERE parent_id =1
GROUP BY parent_id
I have a table with id and parent_id.
I want the count of all sub-entries for a specific entry.
I found several documents about working with graphs/trees in MySQL but I
could not find a solution for my problem.
I can imagine two possibilities, but one is memory intensive and the other
one creates load on updates.
The first is, that I select all entries and then use a procedural language
to determine recursively whether an node is a sub-node of the specific node.
The second is, that I store the sub-node count with each node and when I do
an insert, I walk the tree upwards and increment the node-counts.
Is there a smart solution/best practice for my problem?
Now I can't think of another sentence starting with an i. ;-)