# Check a missing value

The missing value check compares the live and the stored data of one Plant for one Plant-local day. It counts the values, the null values, and the zero values in each source. Then it gives the type of gap. It does not find the cause.

## Start the check

Ask this question in your AI tool. Replace the text in square brackets with your own details:

```
Show the stored 5-minute power and irradiance at [Plant name] from [start time] to [end time] on [date]. Tell me which values are missing.
```

You can also select `missing-value-check` as a prompt. See [Guided checks](https://ai.solarsens.co/docs/concepts/skills.md).

If you do not give a date, the check uses yesterday in the Plant timezone. For a device value, give the device name. If the device name is not clear, the assistant shows the candidates. Select one.

## Types of gap

* **No source data**: the live and the stored data have no value.
* **Live present but stored missing**: the live data has values. The stored data has no value.
* **Stored present but live missing**: the stored data has values. The live data has no value.
* **True zero**: the two sources give 0 at the same times.

A device that shows online can still send old data. The device status is the latest status, not the status on that day.

## Limits

Not checked: work orders, AVA Logger connection, data pipeline runs, status as of D.

Read only when you ask: alarm history.

Missing rows and null values are not zero.