Андрей Ласточкин

SELECT * 
FROM Logon
JOIN 
(
SELECT [Date] D, MIN([Time]) T
FROM Logon
GROUP BY [Date]
) X
ON [Date]=D AND [Time]=T

SELECT uName, 
(
SELECT MIN(uDate) 
FROM Res 
WHERE uName = T.uName AND CAST(uDate AS Date) = D
) FirstDate
FROM 
(
SELECT DISTINCT uName, CAST(uDate AS Date) D
FROM Res
) T