---
title: delta() | Tiger Data Docs
description: Calculate the change in a gauge from a gauge aggregate
---

Early access [1.6.0](https://github.com/timescale/timescaledb-toolkit/releases/tag/1.6.0)

Get the change in a gauge over a time period. This is the simple delta, computed by subtracting the last seen value from the first.

## Samples

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

```
SELECT
    id,
    delta(summary)
FROM (
    SELECT
        id,
        gauge_agg(ts, val) AS summary
    FROM foo
    GROUP BY id
) t
```

## Arguments

The syntax is:

```
delta(
    summary GaugeSummary
) RETURNS DOUBLE PRECISION
```

| Name      | Type           | Default | Required | Description                                                                                                              |
| --------- | -------------- | ------- | -------- | ------------------------------------------------------------------------------------------------------------------------ |
| `summary` | `GaugeSummary` | -       | ✔        | A gauge aggregated created using [`gauge_agg`](/docs/reference/toolkit/counters-and-gauges/gauge_agg/gauge_agg/index.md) |

## Returns

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