# CUME_DIST

The CUME_DIST() function was first introduced with window functions in MariaDB 10.2.0.

## Syntax

```CUME_DIST() OVER (
[ PARTITION BY partition_expression ]
[ ORDER BY order_list ]
)
```

## Description

CUME_DIST() is a window function that returns the cumulative distribution of a given row. The following formula is used to calculate the value:

```(number of rows <= current row) / (total rows)
```

## Examples

```create table t1 (
pk int primary key,
a int,
b int
);

insert into t1 values
( 1 , 0, 10),
( 2 , 0, 10),
( 3 , 1, 10),
( 4 , 1, 10),
( 8 , 2, 10),
( 5 , 2, 20),
( 6 , 2, 20),
( 7 , 2, 20),
( 9 , 4, 20),
(10 , 4, 20);

select pk, a, b,
rank() over (order by a),
percent_rank() over (order by a),
cume_dist() over (order by a)
from t1;
+----+------+------+--------------------------+----------------------------------+-------------------------------+
| pk | a    | b    | rank() over (order by a) | percent_rank() over (order by a) | cume_dist() over (order by a) |
+----+------+------+--------------------------+----------------------------------+-------------------------------+
|  1 |    0 |   10 |                        1 |                     0.0000000000 |                  0.2000000000 |
|  2 |    0 |   10 |                        1 |                     0.0000000000 |                  0.2000000000 |
|  3 |    1 |   10 |                        3 |                     0.2222222222 |                  0.4000000000 |
|  4 |    1 |   10 |                        3 |                     0.2222222222 |                  0.4000000000 |
|  5 |    2 |   20 |                        5 |                     0.4444444444 |                  0.8000000000 |
|  6 |    2 |   20 |                        5 |                     0.4444444444 |                  0.8000000000 |
|  7 |    2 |   20 |                        5 |                     0.4444444444 |                  0.8000000000 |
|  8 |    2 |   10 |                        5 |                     0.4444444444 |                  0.8000000000 |
|  9 |    4 |   20 |                        9 |                     0.8888888889 |                  1.0000000000 |
| 10 |    4 |   20 |                        9 |                     0.8888888889 |                  1.0000000000 |
+----+------+------+--------------------------+----------------------------------+-------------------------------+

select pk, a, b,
percent_rank() over (order by pk),
cume_dist() over (order by pk)
from t1 order by pk;
+----+------+------+-----------------------------------+--------------------------------+
| pk | a    | b    | percent_rank() over (order by pk) | cume_dist() over (order by pk) |
+----+------+------+-----------------------------------+--------------------------------+
|  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),
cume_dist() over (partition by a order by a)
from t1;
+----+------+------+-------------------------------------------------+----------------------------------------------+
| pk | a    | b    | percent_rank() over (partition by a order by a) | cume_dist() over (partition by a order by a) |
+----+------+------+-------------------------------------------------+----------------------------------------------+
|  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 |
+----+------+------+-------------------------------------------------+----------------------------------------------+
```