SQL Find Nearest Effective Date in Related Table - sql

Question

I'll preface this by stating that this problem is similar to SQL Join on Nearest Less Than Date but that the solution there doesn't work for my problem. Instead of selecting a single column, I need the results of a table that is 'filtered' based on the nearest date.
I have three tables. The main table contains time ticket data in the form:
ticketId
ticketNumber
ticketDate
projectId
A secondary table tracks rate schedules for resources on each daily ticket for the project. It looks something like this:
scheduleId
projectId
effectiveDate
There is also a third table that is related to the second that actually contains the applicable rates. Something like this:
scheduleId
straightTime
overTime
Joining the first two tables on projectId (obviously) replicates data for every record in the rate schedule for the project. If I have 3 rate schedules for project 1, then ticket records result in something like:
ticketNumber | ticketDate | projectId | effectiveDate | scheduleId
------------- | ------------ | ----------- | -------------- | ----------
1234 | 2016-06-18 | 25 | 2016-06-01 | 1
1234 | 2016-06-18 | 25 | 2016-06-15 | 2
1234 | 2016-06-18 | 25 | 2016-06-31 | 3
Selecting the effectiveDate into my results is straightforward with the example:
SELECT *
, (SELECT TOP 1 t1.effectiveFrom
FROM dbo.labourRateSchedule t1
WHERE t1.effectiveFrom <= t2.[date] and t1.projectId = t2.projectId
ORDER BY t1.effectiveFrom desc) as effectiveDate
FROM dbo.timeTicket t2
ORDER BY t.date
However, I need to be able to join the ID of dbo.labourRateSchedule onto the third table to get the actual rates that apply. Adding the t1.ID to the SELECT statement does not make it accessible to JOIN into another related table.
I've been trying to JOIN the SELECT statement in the FROM statement but the results are only resulting with the last effectiveDate value instead of one that is closest to the applicable ticketDate.
I would hugely appreciate any help on this!

Answer 1

You can move your subquery to the FROM clause by using CROSS APPLY:
SELECT *
FROM dbo.timeTicket tt
CROSS APPLY
(
SELECT TOP(1) *
FROM dbo.labourRateSchedule lrs
WHERE lrs.projectId = tt.projectId
AND lrs.effectiveFrom <= tt.date
ORDER BY lrs.effectiveFrom desc
) best_lrs
JOIN dbo.schedule s on s.schedule_id = best_lrs.schedule_id
ORDER BY tt.date

Answer 2

Can you try something like this (you should change something, as you didn't post all information).
SELECT A.*, C.*
FROM timeTicket A
INNER JOIN (SELECT * , ROW_NUMBER() OVER (PARTITION BY projectId ORDER BY effectiveFrom DESC) AS RN
FROM labourRateSchedule) B ON A.projectId=B.projectId AND B.RN=1
INNER JOIN YOUR3TABLE C ON B.SCHEDULEID=C.SCHEDULEID

Answer 3

You can do this by CTE and Rank function -
create table timeTicket (ticketId int,
ticketNumber int ,
ticketDate smalldatetime ,
projectId int )
go
create table labourRateSchedule
(scheduleId int,
projectId int,
effectiveDate smalldatetime )
go
create table ApplicableRates
(scheduleId int,
straightTime smalldatetime ,
overTime smalldatetime)
go
insert into timeTicket
select 1 , 1234 ,'2016-06-18' ,25
go
insert into labourRateSchedule
select 1 , 25 ,'2016-06-01'
union all select 2 , 25 ,'2016-06-15'
union all select 3 , 25 ,'2016-06-30'
go
insert into ApplicableRates
select 1 , '2016-06-07' ,'2016-06-07'
union all select 2 , '2016-06-17' ,'2016-06-17'
union all select 3 , '2016-06-22' ,'2016-06-25'
go
with cte
as (
select t1.ticketNumber ,t1.ticketDate ,t1.projectId ,t2.effectiveDate ,t3.scheduleId ,t3.straightTime
,t3.overTime , rank() over ( partition by t1.ticketNumber order by abs (DATEDIFF(day,t1.ticketDate, t2.effectiveDate) ) ) DyaDiff
from timeTicket t1 join labourRateSchedule t2
on t1.projectId = t2.projectId
join ApplicableRates t3
on t2.scheduleId = t3.scheduleId)
select * from cte where DyaDiff = 1