# Filter Permutations

Source: https://userguide.qualytics.io/data-quality-checks/templates/deep-dive/filter-permutations/

A template's **Filter Clause** can use `each()` to turn one template into many checks, one for each value in a list. This applies the same rule across a dimension, such as countries, regions, or product categories, without creating a separate check for every value by hand.

## Syntax

```sql
<field_name> = each('<VALUE_1>', '<VALUE_2>', '<VALUE_3>')
```

`each()` combines with the other filter operators, such as `=`, `>`, `<`, `AND`, and `IN`. Only rule types that accept a filter clause can use it. Volumetric and Freshness, for example, take no filter.

## One Check per Value

A team wants order totals to be checked separately for every country it operates in. Its **Positive** template uses this filter:

```sql
country_code = each('BRA', 'USA', 'ESP', 'CHN')
```

Applying the template to the `TOTAL_AMOUNT` field of the `ORDERS` table creates four checks, one per country. Each check gets the filter for its own value, such as `country_code = 'BRA'`, and runs on its own, so a problem in one country fails only that country's check.

## Several `each()` Clauses

A filter can hold more than one `each()`. Every combination of values becomes its own check.

```sql
region = each('EU', 'US') AND category = each('Retail', 'Wholesale')
```

This creates four checks:

- `region = 'EU' AND category = 'Retail'`
- `region = 'EU' AND category = 'Wholesale'`
- `region = 'US' AND category = 'Retail'`
- `region = 'US' AND category = 'Wholesale'`

## Where `each()` Works

`each()` expands only when checks are created from a template:

- **Creating checks.** Adding a check from a template, or several at once, expands the filter into its permutations.
- **Editing a check.** A check's own filter cannot use `each()`. Saving one fails with *The each() function cannot be used when updating a check's filter. To manage check permutations, update the template filter instead.*
- **Applying the same permutations twice.** When a table or file already has the permutation checks of a template, creating them again fails with a message naming the template to edit instead.

## Changing the Values

Once the permutation checks exist, change their values by editing the **template's** filter. What happens to the checks depends on whether the template is locked:

| Change to the `each()` list | Locked template | Unlocked template |
| --- | --- | --- |
| **Add a value** | Creates a check for the new value on each table or file that already has checks from the list. | The same. |
| **Remove a value** | Deletes the check of that value. | Keeps the check. It stays as it is. |
| **Add `each()` to a filter that had none** | Splits every linked check into one check per value. | Creates no checks. |

A new check is copied from a check the list already has on the same table or file, so it takes that check's fields, tags, and impact metrics. On a locked template, the rest of its definition then follows the template.

> **Tip: Replacing every value of the list**
>
> On a locked template, removing every value and adding new ones in the same save deletes the old checks first, so no check is left to copy and no check is created for the new values. Add the new values and save, then remove the old ones and save again.

### Example

A locked template starts with this filter, applied to one table:

```sql
country_code = each('ITA', 'MEX', 'ESP')
```

- The table gets three checks: Italy, Mexico, and Spain.
- Adding `'BRA'` to the list creates a fourth check, for Brazil.
- Removing `'ESP'` deletes the Spain check.

On an unlocked template, the same edits add the Brazil check, but the Spain check stays.

## See Also

- **Template Overview**

  Every part of a template's Overview: Summary, Description, Definition, and Timeline, plus the page's tabs and actions.

  [Template Overview](https://userguide.qualytics.io/data-quality-checks/templates/deep-dive/template-view/overview/)
- **Template Checks**

  Every check created from the template, across datastores, and how to review the drafts it creates.

  [Template Checks](https://userguide.qualytics.io/data-quality-checks/templates/deep-dive/template-view/checks/)
- **Template Anomalies**

  The anomalies found by every check created from the template, and how to triage them from the template's page.

  [Template Anomalies](https://userguide.qualytics.io/data-quality-checks/templates/deep-dive/template-view/anomalies/)
- **Template Examples**

  Scenarios that show when a template pays off, and whether to lock it.

  [Template Examples](https://userguide.qualytics.io/data-quality-checks/templates/deep-dive/examples/)
- **Template Best Practices**

  How to name, lock, and maintain templates so their checks stay trustworthy.

  [Template Best Practices](https://userguide.qualytics.io/data-quality-checks/templates/deep-dive/best-practices/)
- **Template Permissions**

  Who can create, edit, apply, archive, and export templates.

  [Template Permissions](https://userguide.qualytics.io/data-quality-checks/templates/deep-dive/permissions/)
- **How Templates Work**

  What a template defines, how checks are created from it, and what Locked and Unlocked change.

  [How Templates Work](https://userguide.qualytics.io/data-quality-checks/templates/deep-dive/how-it-works/)

*Last updated: November 10, 2026.*