MySQL n'a pas de fonctionnalité de classement/d'analyse/de fenêtrage.
SELECT tl.locationid, tl.timestamp, tp.name, X, Y, Z
FROM tblPerson tp
JOIN tblLocation tl ON tl.personid = tp.personid
JOIN (SELECT t.personid,
MAX(t.timestamp) AS max_date
FROM tblLocation t
GROUP BY t.personid) x ON x.personid = tl.personid
AND x.max_date = tl.timestamp
SQL Server 2005+ et Oracle 9i+ prennent en charge l'analyse, vous pouvez donc utiliser :
SELECT x.locationid, x.timestamp, x.name, x.X, x.Y, x.Z
FROM (SELECT tl.locationid, tl.timestamp, tp.name, X, Y, Z,
ROW_NUMBER() OVER (PARTITION BY tp.name ORDER BY tl.timestamp DESC) AS rank
FROM tblPerson tp
JOIN tblLocation tl ON tl.personid = tp.personid) x
WHERE x.rank = 1
Utilisation d'une variable pour obtenir la même fonctionnalité que ROW_NUMBER sur MySQL :
SELECT x.locationid, x.timestamp, x.name, x.X, x.Y, x.Z
FROM (SELECT tl.locationid, tl.timestamp, tp.name, X, Y, Z,
CASE
WHEN @name != t.name THEN
@rownum := 1
ELSE @rownum := @rownum + 1
END AS rank,
@name := tp.name
FROM tblLocation tl
JOIN tblPerson tp ON tp.personid = tl.personid
JOIN (SELECT @rownum := NULL, @name := '') r
ORDER BY tp.name, tl.timestamp DESC) x
WHERE x.rank = 1
