MAX Date series before another date grouped - tsql

Question

I have two tables in a stage-gate project management system, one (simplified) table containing a project ID and actual gate dates for each gate, 1-5. In the other I have a historic record of all forecast data; Projected Revenue, Projected Margins, Forecast Year, etc. Each time a forecast is updated, it records the new forecast values, the time stamp of the change, and the project ID. The requirement is to retrieve all metric values for the latest update prior to the actual gate date recorded in the first table. An example, Project 100 has a Gate 2 date of 2014-12-18. I need to retrieve the most recent values prior to that date.
Gate Date Table:
ProjectID InternalGate2
--------- -------------
100 2014-12-18
2000 2013-01-15
Historic Metric Table:
ProjectID Metric MetricYear LastUpdated MetricValue
--------- ------ ---------- ----------- -----------
100 Sales 2015 2013-09-05 125000
100 Sales 2016 2013-09-05 230000
100 GM 2015 2013-09-05 .48
100 GM 2016 2013-09-05 .49
100 Sales 2015 2014-05-26 200000
100 Sales 2016 2014-05-26 300000
100 GM 2015 2014-05-26 .50
100 GM 2016 2014-05-26 .51
100 Sales 2015 2015-01-28 300000
100 Sales 2016 2015-01-28 400000
100 GM 2015 2015-01-28 .55
100 GM 2016 2015-01-28 .56
2000 Sales 2014 2012-11-23 200000
2000 Sales 2015 2012-11-23 300000
2000 Sales 2016 2012-11-23 310000
2000 GM 2014 2012-11-23 .75
2000 GM 2015 2012-11-23 .77
2000 GM 2016 2012-11-23 .77
2000 Sales 2015 2013-02-11 450000
2000 Sales 2016 2013-02-11 450000
2000 Sales 2017 2013-02-11 500000
2000 GM 2015 2013-02-11 .68
2000 GM 2016 2013-02-11 .69
2000 GM 2017 2013-02-11 .70
For this example the results set would be the four rows for Project 100 with the LastUpdated Date of 2014-05-26 as this was the last update prior to 2014-12-18 and the first six rows of data for Project 2000 updated 2012-11-23.
Any guidance would be greatly appreciated.

Answer 1

The CTE could be a subquery if you prefer, but this works, basically just using two joins.
;WITH CTE as
(select h.ProjectID,MAX(LastUpdated) as LatestUpdate
from Historic h
inner join Gate g
on h.ProjectID = g.ProjectID
and h.LastUpdated <= g.InternalGate2
group by h.ProjectID)
select ProjectID,LastUpdated
from Historic h
inner join CTE c
on h.ProjectID = c.ProjectID
and h.LastUpdated = c.LatestUpdate