> For the complete documentation index, see [llms.txt](https://docs.decube.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.decube.io/data-quality-v2/monitor-types.md).

# Monitor Types

Pick the monitor type that answers the question you have about your data.

## Choosing a monitor type

Each monitor type answers one question about one asset. Start from the question, then open that type's page for what it checks, what you configure, and a worked example.

| The question you have                                 | Monitor type                                                                                   |
| ----------------------------------------------------- | ---------------------------------------------------------------------------------------------- |
| Did the data arrive on time, or has it gone stale?    | [Freshness (SLA and Staleness)](/data-quality-v2/monitor-types/freshness-sla-and-staleness.md) |
| Did the expected number of rows land?                 | [Volume](/data-quality-v2/monitor-types/volume.md)                                             |
| Does this column hold the values it should?           | [Field Health](/data-quality-v2/monitor-types/field-health.md)                                 |
| Does this business rule hold, possibly across tables? | [Custom SQL](/data-quality-v2/monitor-types/custom-sql.md)                                     |

### What each type works on

* **Freshness and Volume** watch a whole table and produce one measurement per run, compared against a Threshold.
* **Field Health** watches a single column, checks every row against a rule, and compares the number of failing rows against a Tolerance. Applicability depends on the column's type, covered in the Field Health overview.
* **Custom SQL** runs a query you write, so it is the type to reach for when the check spans more than one table.

### Creating many at once

Templates apply one configuration across many tables, currently for Freshness monitors.

{% content-ref url="/pages/gTbg3448XNHbTM66M7h5" %}
[Create monitors in bulk with Templates](/data-quality-v2/create-monitors-in-bulk-with-templates.md)
{% endcontent-ref %}

## Applicable assets

Every monitor type runs against one kind of asset. Use this table to pick the right asset in Step 1 of the monitor wizard.

| Monitor type                    | Check                                       | Applicable asset                                                                    |
| ------------------------------- | ------------------------------------------- | ----------------------------------------------------------------------------------- |
| Freshness                       | SLA, Staleness                              | Table or view                                                                       |
| Volume                          | Count Delta, Percentage Delta               | Table or view                                                                       |
| Field Health — Numeric checks   | Average, Minimum, Maximum, Sum              | Numeric column                                                                      |
| Field Health — Numerical Range  | Numerical Range                             | Numeric column                                                                      |
| Field Health — Condition checks | Zero                                        | Numeric column                                                                      |
| Field Health — Condition checks | Null, Unique                                | Column of any type                                                                  |
| Field Health — String checks    | String Length, Regex Match, Regex Not Match | String column                                                                       |
| Field Health — Value set checks | Value In, Value Not In                      | String column                                                                       |
| Field Health — Temporal checks  | Is Before, Is After                         | Date or timestamp column                                                            |
| Custom SQL                      | Your own query                              | Data source, optionally associated with up to 10 tables or columns from that source |

{% hint style="warning" %}
Monitors run queries against the physical data in your source, so they only apply to tables, views, and columns that exist in a connected warehouse or database. Virtual tables and virtual columns (for example, dbt models or Tableau data sources ingested by a transformation or BI connector), and any asset under a [virtual source](/virtual-sources-and-objects/virtual-sources.md), are not applicable assets for monitors. To monitor a dbt model, add the monitor to the table or view that the model materializes in your warehouse.
{% endhint %}

Many sources don't expose last-modified time or row-count metadata for views. Where that metadata is missing, Decube doesn't offer metadata-based detection, so a Freshness or Volume monitor on a view uses column-based detection, or full table count for Volume.