Calculate rank without gaps. This function assigns a rank to each row within a partition, with tied values receiving the same rank and no numbers skipped.
DENSE_RANK() OVER (
[ PARTITION BY partition_expression ]
[ ORDER BY order_list ]
)DENSE_RANK() is a that displays the number of a given row, starting at one and following the sequence of the window function, with identical values receiving the same result. Unlike the function, there are no skipped values if the preceding results are identical. It is also similar to the function except that in that function, identical values will receive a different row number for each result.
The distinction between DENSE_RANK(), and :
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CREATE TABLE student(course VARCHAR(10), mark int, name varchar(10));
INSERT INTO student VALUES
('Maths', 60, 'Thulile'),
('Maths', 60, 'Pritha'),
('Maths', 70, 'Voitto'),
('Maths', 55, 'Chun'),
('Biology', 60, 'Bilal'),
('Biology', 70, 'Roger');
SELECT
RANK() OVER (PARTITION BY course ORDER BY mark DESC) AS rank,
DENSE_RANK() OVER (PARTITION BY course ORDER BY mark DESC) AS dense_rank,
ROW_NUMBER() OVER (PARTITION BY course ORDER BY mark DESC) AS row_num,
course, mark, name
FROM student ORDER BY course, mark DESC;
+------+------------+---------+---------+------+---------+
| rank | dense_rank | row_num | course | mark | name |
+------+------------+---------+---------+------+---------+
| 1 | 1 | 1 | Biology | 70 | Roger |
| 2 | 2 | 2 | Biology | 60 | Bilal |
| 1 | 1 | 1 | Maths | 70 | Voitto |
| 2 | 2 | 2 | Maths | 60 | Thulile |
| 2 | 2 | 3 | Maths | 60 | Pritha |
| 4 | 3 | 4 | Maths | 55 | Chun |
+------+------------+---------+---------+------+---------+