SQL server implements recursive query.

SQL server implements recursive query.

This example describes how SQL server implements recursive queries. We will share this with you for your reference. The details are as follows:

Sometimes recursive queries are required for tree-structured data. After searching for the data on the Internet and referring to the articles of great gods, we found it quite simple to use it as a small note for future use.

SQL server supports recursive query through CTE, which is useful for querying data in a tree or hierarchy.

The general tree table structure is as follows. I believe everyone is familiar with it.

Id	Title	Pid
1	Level 1 Node	0
2	Level 2 node	1
3	Level 3 Node	2
4	Level 4 node	3
5	Level 5 Node	4

The code below

---------- SQL server recursive query ------------ query all upper-level nodes with uCte as (select. id,. title,. pid from tree_table a where id = 3 -- current node union all select k. id, k. title, k. pid from tree_table k inner join uCte c on c. pid = k. id) select * from uCte; -- Query all upper-level nodes with dCte as (select. id,. title,. pid from tree_table a where id = 3 -- current node union all select k. id, k. title, k. pid from tree_table k inner join dCte c on c. id = k. pid) select * from dCte;