TSQL Recursive Query with Count - sql

Question

I have a recursive query that I have working for the most part. Here is what I have so far:
DECLARE #table TABLE(mgrQID VARCHAR(64), QID VARCHAR(64), NTID VARCHAR(64), FullName VARCHAR(64), lvl int, dt DATETIME, countOfDirects INT)
WITH empList(mgrQID, QID, NTID, FullName, lvl, metadate)
AS
(
SELECT TOP 1 mgrQID, QID, NTID, FirstName+' '+LastName, 0, Meta_LogDate
FROM dbo.EmployeeTable_Historical
WHERE QID IN (SELECT director FROM dbo.attritionDirectors) AND Meta_LogDate <= #pit
ORDER BY Meta_LogDate DESC
UNION ALL
SELECT b.mgrQID, b.QID, b.NTID, b.FirstName+' '+b.LastName, lvl+1, b.Meta_LogDate
FROM empList a
CROSS APPLY dbo.Fetch_DirectsHistorical_by_qid(a.QID, #pit)b
)
INSERT INTO #table(mgrQID, QID, NTID, FullName, lvl, dt)
SELECT empList.mgrQID ,
empList.QID ,
empList.NTID ,
empList.FullName ,
empList.lvl ,
empList.metadate
FROM empList
ORDER BY lvl
OPTION(MAXRECURSION 10)
Now, #table has a list of QIDs in it. I need to then join my employee table and find out how many people report to each of those QID's.
So, there will need to be an UPDATE that happens to #table which provides the count of employees that report to each of those QID's.
Here is the catch.. The employee table is a historical table that can contain multiple records for the same people. Any time a piece of their information is updated a new record is created with those changes.
If I wanted to pull the most recent record for some one right now, i would use this:
SELECT TOP 1 E.*
FROM employeeTable_historical AS E
WHERE E.qid = A.[subQID]
AND CONVERT (DATE, GETDATE()) > CONVERT (DATE, E.[Meta_LogDate])
ORDER BY meta_logDate DESC
The question..
I need to be able to get the count of employees in the historical table that report directly to each QID in the #table. The historical table has a column called mgrQID. Is there a way I can get this count in the original recursive query?

Answer 1

I would recommend first that you look at the approach you're taking. The historical table you're dealing with will certainly need to select the greatest Meta_LogDate for any given employee, but in the structure you've set up here, you'll never select more than one record from matching attritionDirectors, thanks to the TOP 1 in your anchor query. As such, I'd recommend a lightweight function on which you base your query:
create function dbo.EmployeesAsOf(#date datetime)
returns table
as return
select mgrQID, QID, NTID, FirstName, LastName, Meta_LogDate
from dbo.EmployeeTable_Historical A
where Meta_LogDate = (select max(Meta_LogDate) from dbo.EmployeeTable_Historical B where A.QID = B.QID and Meta_LogDate <= #date)
This will allow you to get the most recent record for anyone, and as long as EmployeeTable_Historical has an index on (QID, Meta_LogDate), this view will perform well.
Having said that, looking at your recursive query, you'll likely want to tweak the recursive query somewhat:
create function empList(#thisDate datetime)
returns #emptbl table (
mgrQID varchar(10)
, QID varchar(10)
, NTID varchar(10)
, Name varchar(21)
, Meta_LogDate datetime
, DirectsThisMany int
)
as
begin
;with empList AS (
select E.mgrQID, E.QID, E.NTID, E.FirstName + ' ' + E.LastName AS Name, E.Meta_LogDate
from dbo.EmployeesAsOf(#thisDate) E
inner join dbo.attritionDirectors D on E.QID = D.QID
union all
select E.mgrQID, E.QID, E.NTID, E.FirstName + ' ' + E.LastName AS Name, E.Meta_LogDate
from dbo.EmployeesAsOf(#thisDate) E
inner join empList D on E.mgrQID = D.QID
)
insert into #emptbl
select A.mgrQID, A.QID, A.NTID, A.Name, A.Meta_LogDate, count(b.QID) AS DirectsThisMany
from empList A
left join empList B on A.QID = B.mgrQID
group by A.mgrQID, A.QID, A.NTID, A.Name, A.Meta_LogDate
return
end
In this way, you'll be able to feed in any date and get a read of the tables, including counts from history as of that date. The self-join of the CTE is what enables us to get the current count of directs, as one can't use aggregates in the CTE. This function is easy to use, and the indexing strategy should become apparent by looking at the query plan in SSMS. A simple SELECT * FROM EmpList(GETDATE()) will give the current situation.