| b    | pct_rank     | cume_dist    |
+----+------+------+--------------+--------------+
|  1 |    0 |   10 | 0.0000000000 | 0.1000000000 |
|  2 |    0 |   10 | 0.1111111111 | 0.2000000000 |
|  3 |    1 |   10 | 0.2222222222 | 0.3000000000 |
|  4 |    1 |   10 | 0.3333333333 | 0.4000000000 |
|  5 |    2 |   20 | 0.4444444444 | 0.5000000000 |
|  6 |    2 |   20 | 0.5555555556 | 0.6000000000 |
|  7 |    2 |   20 | 0.6666666667 | 0.7000000000 |
|  8 |    2 |   10 | 0.7777777778 | 0.8000000000 |
|  9 |    4 |   20 | 0.8888888889 | 0.9000000000 |
| 10 |    4 |   20 | 1.0000000000 | 1.0000000000 |
+----+------+------+--------------+--------------+

select pk, a, b,
    percent_rank() over (partition by a order by a) as pct_rank,
    cume_dist() over (partition by a order by a) as cume_dist
from t1;
+----+------+------+--------------+--------------+
| pk | a    | b    | pct_rank     | cume_dist    |
+----+------+------+--------------+--------------+
|  1 |    0 |   10 | 0.0000000000 | 1.0000000000 |
|  2 |    0 |   10 | 0.0000000000 | 1.0000000000 |
|  3 |    1 |   10 | 0.0000000000 | 1.0000000000 |
|  4 |    1 |   10 | 0.0000000000 | 1.0000000000 |
|  5 |    2 |   20 | 0.0000000000 | 1.0000000000 |
|  6 |    2 |   20 | 0.0000000000 | 1.0000000000 |
|  7 |    2 |   20 | 0.0000000000 | 1.0000000000 |
|  8 |    2 |   10 | 0.0000000000 | 1.0000000000 |
|  9 |    4 |   20 | 0.0000000000 | 1.0000000000 |
| 10 |    4 |   20 | 0.0000000000 | 1.0000000000 |
+----+------+------+--------------+--------------+

URL: https://mariadb.com/kb/en/percent_rank/https://mariadb.com/kb/en/percent_rank/