SQL statement - join based on date - sql-server

Question

I need to write a statement joining two tables based on dates.
Table 1 contains time recording entries.
+----+-----------+--------+---------------+
| ID | Date | UserID | DESC |
+----+-----------+--------+---------------+
| 1 | 1.10.2010 | 5 | did some work |
| 2 | 1.10.2011 | 5 | did more work |
| 3 | 1.10.2012 | 4 | me too |
| 4 | 1.11.2012 | 4 | me too |
+----+-----------+--------+---------------+
Table 2 contains the position of each user in the company. The ValidFrom date is the date at which the user has been or will be promoted.
+----+-----------+--------+------------+
| ID | ValidFrom | UserID | Pos |
+----+-----------+--------+------------+
| 1 | 1.10.2009 | 5 | PM |
| 2 | 1.5.2010 | 5 | Senior PM |
| 3 | 1.10.2010 | 4 | Consultant |
+----+-----------+--------+------------+
I need a query which outputs table one with one added column which is the position of the user at the time the entry has been made. (the Date column)
All date fileds are of type date.
I hope someone can help. I tried a lot but don't get it working.

Answer 1

Try this using a subselect in the where clause:
SQL Fiddle
MS SQL Server 2008 Schema Setup:
CREATE TABLE TimeRecord
(
ID INT,
[Date] Date,
UserID INT,
Description VARCHAR(50)
)
INSERT INTO TimeRecord
VALUES (1,'2010-01-10',5,'did some work'),
(2, '2011-01-10',5,'did more work'),
(3, '2012-01-10', 4, 'me too'),
(4, '2012-11-01',4,'me too')
CREATE TABLE UserPosition
(
ID Int,
ValidFrom Date,
UserId INT,
Pos VARCHAR(50)
)
INSERT INTO UserPosition
VALUES (1, '2009-01-10', 5, 'PM'),
(2, '2010-05-01', 5, 'Senior PM'),
(3, '2010-01-10', 4, 'Consultant ')
Query 1:
SELECT TR.ID,
TR.[Date],
TR.UserId,
TR.Description,
UP.Pos
FROM TimeRecord TR
INNER JOIN UserPosition UP
ON UP.UserId = TR.UserId
WHERE UP.ValidFrom = (SELECT MAX(ValidFrom)
FROM UserPosition UP2
WHERE UP2.UserId = UP.UserID AND
UP2.ValidFrom <= TR.[Date])
Results:
| ID | Date | UserId | Description | Pos |
|----|------------|--------|---------------|-------------|
| 1 | 2010-01-10 | 5 | did some work | PM |
| 2 | 2011-01-10 | 5 | did more work | Senior PM |
| 3 | 2012-01-10 | 4 | me too | Consultant |
| 4 | 2012-11-01 | 4 | me too | Consultant |

Answer 2

You can do it using OUTER APPLY:
SELECT ID, [Date], UserID, [DESC], x.Pos
FROM table1 AS t1
OUTER APPLY (
SELECT TOP 1 Pos
FROM table2 AS t2
WHERE t2.UserID = t1.UserID AND t2.ValidFrom <= t1.[Date]
ORDER BY t2.ValidFrom DESC) AS x(Pos)
For every row of table1 OUTER APPLY operation fetches all table2 rows of the same user that have a ValidFrom date that is older or the same as [Date]. These rows are sorted in descending order and the most recent of these is finally returned.
Note: If no match is found by the OUTER APPLY sub-query then a NULL value is returned, meaning that no valid position exists in table2 for the corresponding record in table1.
Demo here

Answer 3

This works by using a rank function and subquery. I tested it with some sample data.
select sub.ID,sub.Date,sub.UserID,sub.Description,sub.Position
from(
select rank() over(partition by t1.userID order by t2.validfrom desc)
as 'rank', t1.ID as'ID',t1.Date as'Date',t1.UserID as'UserID',t1.Descr
as'Description',t2.pos as'Position', t2.validfrom as 'validfrom'
from temployee t1 inner join jobs t2 on -- replace join tables with your own table names
t1.UserID=t2.UserID
) as sub
where rank=1

Answer 4

This query would work
select t1.*,t2.pos from Table1 t1 left outer join Table2 t2 on
t1.Date=t2.Date and t1.UserID=t2.UserID