DECLARE @persons TABLE(
personid INT,
version INT)

INSERT @persons
VALUES(1,1),(1,2),(1,3),(2,1),(2,2),(3,1),(4,1),(4,2)

SELECT
personid,
maxversion = MAX(version)
FROM 
@persons
GROUP BY personid
ORDER BY personid

DECLARE @persons TABLE(
personid INT,
version INT);

INSERT @persons
VALUES(1,1),(1,2),(1,3),(2,1),(2,2),(3,1),(4,1),(4,2);

SELECT
personid,
maxversion = MAX(version)
FROM 
@persons
GROUP BY personid
ORDER BY personid;

WITH BaseData AS (
SELECT
    personid,
    version,
    ROW_NUMBER() OVER (PARTITION BY personid ORDER BY version DESC) rn
FROM
    @persons
)
SELECT
    personid,
    version
FROM
    BaseData
where
    rn = 1;