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Create Table table_name(Student VARCHAR(50), Time_ TIME);
Insert Into table_name Values('A','5:00'),
('B','7:00'),
('A','8:00'),
('C','9:00'),
('D','10:00'),
('E','11:00'),
('D','12:00');
Records: 7 Duplicates: 0 Warnings: 0
SELECT Student, Time_,
SUM(flag) OVER (ORDER BY Time_) AS expected_count
FROM
(
SELECT *,
CASE
WHEN EXISTS(SELECT 1 FROM table_name D WHERE D.Student = T.Student AND D.Time_<T.Time_)
THEN 0 ELSE 1
END AS flag
FROM table_name T
) D
ORDER BY Time_
| Student | Time_ | expected_count |
|---|---|---|
| A | 05:00:00 | 1 |
| B | 07:00:00 | 2 |
| A | 08:00:00 | 2 |
| C | 09:00:00 | 3 |
| D | 10:00:00 | 4 |
| E | 11:00:00 | 5 |
| D | 12:00:00 | 5 |