select the latest result based on DateTime field - sql

Question

I have a simple table with only 4 fields.
http://sqlfiddle.com/#!3/06d7d/1
CREATE TABLE Assessment (
id INTEGER IDENTITY(1,1) PRIMARY KEY,
personId INTEGER NOT NULL,
dateTaken DATETIME,
outcomeLevel VARCHAR(2)
)
INSERT INTO Assessment (personId, dateTaken, outcomeLevel)
VALUES (1, '2014-04-01', 'L1')
INSERT INTO Assessment (personId, dateTaken, outcomeLevel)
VALUES (1, '2014-04-05', 'L2')
INSERT INTO Assessment (personId, dateTaken, outcomeLevel)
VALUES (2, '2014-04-03', 'E3')
INSERT INTO Assessment (personId, dateTaken, outcomeLevel)
VALUES (2, '2014-04-07', 'L1')
I am trying to select for each "personId" their latest assessment result based on the dateTaken.
So my desired output for the following data would be.
[personId, outcomeLevel]
[1, L2]
[2, L1]
Thanks,
Danny

Answer 1

Try this:
;with cte as
(select personId pid, max(dateTaken) maxdate
from assessment
group by personId)
select personId, outcomeLevel
from assessment a
inner join cte c on a.personId = c.pid
where c.maxdate = a.dateTaken
order by a.personId

Answer 2

;with Cte as (Select personId,outcomeLevel, C= ROW_NUMBER()
over(PARTITION By personId Order By dateTaken desc)
From #Assessment
)
Select * from cte where C=1
Sample here

Answer 3

SELECT asst.personId,
asst.outcomeLevel
FROM dbo.Assessment asst
WHERE asst.dateTaken=(SELECT MAX(ast.dateTaken)
FROM assessment ast
WHERE asst.personid=ast.personId)
ORDER BY asst.personId
Result will be like this
personId outcomeLevel
1 L2
2 L1

Answer 4

Here is a possible solution using common table expression:
WITH cte AS (
SELECT
ROW_NUMBER() OVER (PARTITION BY personId ORDER BY dateTaken DESC) AS rn
, personId
, outcomeLevel
FROM
[dbo].[Assessment]
)
SELECT
personId
, outcomeLevel
FROM
cte
WHERE
rn = 1
About CTEs
A common table expression (CTE) can be thought of as a temporary result set that is defined within the execution scope of a single SELECT, INSERT, UPDATE, DELETE, or CREATE VIEW statement. A CTE is similar to a derived table in that it is not stored as an object and lasts only for the duration of the query. Unlike a derived table, a CTE can be self-referencing and can be referenced multiple times in the same query. From MSDN: Using Common Table Expressions

Answer 5

try this:
SELECT a.personId, a.outcomeLevel
FROM Assessment a
INNER JOIN
(
SELECT max(dateTaken) as datetaken1, personId
FROM Assessment
GROUP BY personId ) b
ON a.dateTaken = b.datetaken1
demo: http://sqlfiddle.com/#!3/06d7d/9
Idea is to first derive a table with the max dates per person and then join that with the original table on the date field so you can get the outcome level for this maxed date...

Answer 6

This should work perfectly without cte :
SELECT [Table4].[personId], [Table4].[outcomeLevel]
FROM (
SELECT [Table1].[personId]
FROM [Assessment] AS [Table1]
GROUP BY [Table1].[personId]
) AS [Table2]
CROSS APPLY (
SELECT TOP (1) [Table3].[personId], [Table3].[outcomeLevel], [Table3].[dateTaken]
FROM [Assessment] AS [Table3]
WHERE [Table2].[personId] = [Table3].[personId]
ORDER BY [Table3].[dateTaken] DESC
) AS [Table4]
ORDER BY [Table4].[dateTaken] DESC