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I have a table with self referencing relation,
ID parentID UserId Title
1 null 100 A
2 1 100 B
3 2 100 C
4 2 100 D
5 null 100 E
6 5 100 F
I want to update UserId from 100 to 101 for all records with ID=1 and its children, so I want to have
ID parentID UserId Title
1 null 101 A
2 1 101 B
3 2 101 C
4 2 101 D
5 null 100 E
6 5 100 F
How can I do it in T-SQL?
633
First, execute the anchor member to form the base result set (R0), use this result for the next iteration. Second, execute the recursive member with the input result set from the previous iteration (Ri-1) and return a sub-result set (Ri) until the termination condition is met.
Recursion is achieved by WITH statement, in SQL jargon called Common Table Expression (CTE). It allows to name the result and reference it within other queries sometime later. Naming the result and referencing it within other queries.
Recursion occurs because of the query referencing the CTE itself based on the Employee in the Managers CTE as input. The join then returns the employees who have their managers as the previous record returned by the recursive query. The recursive query is repeated until it returns an empty result set.
A recursive CTE references itself. It returns the result subset, then it repeatedly (recursively) references itself, and stops when it returns all the results. FROM cte_name; Again, at the beginning of your CTE is the WITH clause.
You probably want to use a common table expression which allows you to generate recursive queries.
eg:
;with cte as
(
select * from yourtable where id=1
union all
select t.* from cte
inner join yourtable t on cte.id = t.parentid
)
update yourtable
set userid = 101
where id in (select id from cte)
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