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i have a self related table myTable like :
ID | RefID
----------
1 | NULL
2 | 1
3 | 2
4 | NULL
5 | 2
6 | 5
7 | 5
8 | NULL
9 | 7
i need to get leaf rows on any depth
based on the table above, the result must be :
ID | RefID
----------
3 | 2
4 | NULL
6 | 5
8 | NULL
9 | 7
thank you
PS: the depth may vary , here is very small example
565
Use the COUNT aggregate function to count the number of rows in a table. This function takes the name of the column as its argument (e.g., id ) and returns the number of rows for this particular column in the table (e.g., 5).
The leaf level is the level just above the data; it contains one index row for each data row. Index rows on the index page are stored in key value order.
In Sql Server an index is made up of a set of pages (index nodes) that are organized in a B+ tree structure. This structure is hierarchical in nature. The top node is called the ROOT node (Root Page). The bottom level of nodes in the index are called the leaf nodes (leaf Pages).
Each leaf node is stored in a database block or page; that is, the database's smallest storage unit. All index blocks are of the same size—typically a few kilobytes. The database uses the space in each block to the extent possible and stores as many index entries as possible in each block.
Try:
SELECT id,
refid
FROM mytable t
WHERE NOT EXISTS (SELECT 1
FROM mytable
WHERE refid = t.id)
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