> ## 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.

# delta()

> Calculate the change in a counter from a counter aggregate

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

Get the change in a counter over a time period. This is the simple delta, computed by subtracting the last seen value
from the first, after accounting for resets.

## Samples

Get the change in each counter over the entire time interval in table `foo`.

```sql theme={"dark"}
SELECT
    id,
    delta(summary)
FROM (
    SELECT
        id,
        counter_agg(ts, val) AS summary
    FROM foo
    GROUP BY id
) t
```

## Arguments

The syntax is:

```sql theme={"dark"}
delta(
    summary CounterSummary
) RETURNS DOUBLE PRECISION
```

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

## Returns

| Column | Type             | Description                                          |
| ------ | ---------------- | ---------------------------------------------------- |
| delta  | DOUBLE PRECISION | The change in the counter over the bucketed interval |

[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