# percentile_disc

Selects an actual input value at the requested percentile. Unlike
[`percentile_cont`](https://coordinatordb.com/docs/reference/functions/aggregate-functions/percentile-cont), this function does not interpolate
between values. `NULL` values are skipped.

**Syntax**

```text
percentile_disc(fraction) WITHIN GROUP (ORDER BY value [ASC|DESC])
percentile_disc(fraction, value[, descending])
```

**Arguments**

* `fraction` — A number from zero through one, independent of the group's input
  rows. It is validated even when the input is empty.
* `value` — An ordered SQL value. Comparison uses its type and collation;
  `NULL` values are skipped.
* `descending` — An optional constant boolean selecting descending order in
  the direct form. The default order is ascending.

Use `FILTER` to select input rows. Window calls with `OVER` are not supported.

**Returned value**

The original input value at position `ceil(fraction * count)`, counting from
one. A fraction of zero selects the first value. A `NULL` fraction or no
non-`NULL` inputs returns `NULL`.

**Examples**

```sql
CREATE TABLE readings (value Int32);
INSERT INTO readings VALUES (10), (20), (30), (40), (NULL);
```

```sql
SELECT percentile_disc(0.5) WITHIN GROUP (ORDER BY value)
FROM readings
FORMAT csv;
```

```text
20
```