Users
with: RowID, EmployeeId, and MangerId
. @RowCount
is the number of records in this table and #EmpMgr
is a cursor for this table.Below is the relevant sql code that I would like to convert from a cursor based operation to a set based operation.
WHILE @RowCount <= @NumberRecords --loop through each record in Users table
BEGIN
SET @EmpId = (SELECT EmployeeId FROM #EmpMgr WHERE RowID = @RowCount)
SET @MgrId = (SELECT ManagerId FROM #EmpMgr WHERE RowID = @RowCount)
INSERT INTO [Trees].[DirectReports](EmployeeId, ManagerId, Depth)
SELECT c.EmployeeId, p.ManagerId, p.Depth + c.Depth + 1
FROM Trees.DirectReports p join Trees.DirectReports c
WHERE p.EmployeeId = @MgrId AND c.ManagerId = @EmpId
SET @RowCount = @RowCount + 1
END
So I'd really like to figure out how to do this as a set query because I know it would be much faster that way but my brain isn't quite making the proper connections today to figure it out.
*Note that to answer this question you will need to already understand how closure tables work. Otherwise the above probably won't make sense.
Found what I was looking for with the help of a couple other posts. The main answer is this:
WITH cte AS
(
SELECT LegacyId ancestor, LegacyId descendant, 0 depth FROM Users
UNION ALL
SELECT cte.ancestor, u.LegacyId descendant, cte.depth + 1 depth
FROM dbo.Users u JOIN cte ON u.ManagerId = cte.descendant
)
select * from cte
However, what threw me off at first was that there was some bad data causing circular dependencies. I was able to use the following query to identify where those instances were:
with cte (id,pid,list,is_cycle)
as
(
select legacyid id, managerid pid,',' + cast (legacyid as varchar(max)) + ',',0
from users
union all
select u.legacyid id,
u.managerid pid,
cte.list + cast(u.legacyid as varchar(10)) + ',' ,case when cte.list like '%,' + cast (u.legacyid as varchar(10)) + ',%' then 1 else 0 end
from cte join users u on u.managerid = cte.id
where cte.is_cycle = 0
)
select *
from cte
where is_cycle = 1
Once I corrected the cyclical data everything worked great. Check out the following SO posts for more information as these are what I used to come up with my solution: Is there a way to detect a cycle in Hierarchical Queries in SQL Server? and How can I create a closure table using data from an adjacency list?