> ## Documentation Index
> Fetch the complete documentation index at: https://mintlify-poc.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# num_changes()

> Get the number of times a counter changed from a counter aggregate

<Icon icon="tag" iconType="duotone" /> Since [1.3.0][toolkit-1.3.0]

Get the number of times the counter changed during the period summarized by the counter aggregate. Any change is
counted, including resets to zero.

## Samples

Get the number of times the counter changed over each 15-minute interval.

```sql theme={"dark"}
SELECT
    id,
    bucket,
    num_changes(summary)
FROM (
    SELECT
        id,
        time_bucket('15 min'::interval, ts) AS bucket,
        counter_agg(ts, val) AS summary
    FROM foo
    GROUP BY id, time_bucket('15 min'::interval, ts)
) t
```

## Arguments

The syntax is:

```sql theme={"dark"}
num_changes(
    summary CounterSummary
) RETURNS BIGINT
```

| Name      | Type             | Default | Required | Description                                                  |
| --------- | ---------------- | ------- | -------- | ------------------------------------------------------------ |
| `summary` | `CounterSummary` | -       | ✔        | A counter summary created using [`counter_agg`][counter-agg] |

## Returns

| Column       | Type   | Description                             |
| ------------ | ------ | --------------------------------------- |
| num\_changes | BIGINT | The number of times the counter changed |

[counter-agg]: /api-reference/timescaledb-toolkit/counters-and-gauges/counter_agg/counter_agg

[toolkit-1.3.0]: https://github.com/timescale/timescaledb-toolkit/releases/tag/1.3.0