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# Reuse values and SQL with Parameters and snippets

> Define a reusable value (Parameter) or SQL block (Snippet) once in Mammoth and use it in filters, formulas and SQL rules across every pipeline.

A Parameter is a named value, and a Snippet is a reusable block of SQL. You define each once and reference it in every pipeline that needs it; when you change it, every pipeline that uses it is flagged stale so you can rerun them. Open them under **Data** in the left sidebar, on the **Parameters** tab; Project Admins and Project Editors can create and change them, and Parameters are included on every plan.

## What a Parameter is

A **Parameter** is a named value (a number, a text string or a date) that you plug into pipeline conditions, filters, calculations and step values. Instead of typing `100` into ten filters, you define a `Max_Units` parameter with value `100` and reference `{Max_Units}` everywhere. To change the threshold, you update the parameter once.

| Type | Use for | Example value |
| --- | --- | --- |
| **Number** | Thresholds, counts, amounts | `100`, `0.75` |
| **Text** | Status values, category names, flags | `"Active"`, `"Yes"` |
| **Date** | Cut-off dates, reporting periods | `2026-04-01` |

To reference a parameter, put curly braces around its name:

```plaintext
{Max_Units}
```

For example, a SQL rule like `WHERE Discount < {Max_Discount}` substitutes the parameter's current value at runtime. In most steps you don't type the braces: you pick the parameter from a picker, and Mammoth shows it as a `{Max_Units}` token.

## What a Snippet is

A **Snippet** is a reusable block of SQL code. Where parameters hold one value, snippets hold logic, such as a SQL fragment, a subquery or a WHERE clause. You embed a snippet with double braces:

```sql
SELECT {{column_list}} FROM orders WHERE {{standard_date_filter}}
```

Snippets can reference parameters, so you can parameterise complex logic. A snippet's language is always SQL.

These Snippets live in the Data Library. The **Snippets** entry in Ask's navigation is unrelated: there, a snippet is a canvas of charts, numbers and notes saved from your chats.

## Find Parameters and snippets in the library

Click **Data** in the left sidebar, then the **Parameters** tab in the Data Library tab bar (after **Datasets**, **Connections** and **Automations**). It shows every parameter and snippet for the current project.

![Parameters library with a General group of three parameters, a Search box, Filter, and New Parameter button, and Name, Value, Subtype, and Uses columns](https://mammoth.io/docs/images/20260418_190007_parameters-list1.webp)

The library groups items by category. Each row shows:

| Column | What it shows |
| --- | --- |
| **Name** | The identifier used in `{name}` references |
| **Description** | What this parameter represents |
| **Value** | The current value |
| **Subtype** | Number, Text or Date (for parameters); SQL (for snippets) |
| **Uses** | How many pipelines reference this parameter or snippet |

Stale rows are highlighted. A banner at the top, for example "2 parameters were updated. Rerun affected pipelines to apply changes.", offers **Rerun stale pipelines**.

### Search and filter the library

- Use the **Search parameters** box to find by name.
- Click **Filter** to narrow by type (parameters or snippets), subtype (Date, Number, Text, SQL) or category.
- **Group by** switches the table between None, Category and Type. Category is the default.
- The **Learn more** icon links to help.

## Who can manage Parameters and snippets

Creating, editing, duplicating and deleting parameters and snippets needs the **Manage Parameters and Snippets** permission, which **Project Admin** and **Project Editor** have. A **Project Viewer** can open the library and read every item, but **New Parameter** is disabled, with the tooltip "Your role doesn't have permission to perform this action". See [Members, roles and custom roles](https://mammoth.io/docs/learn/workspace/members-and-roles/).

## Create a Parameter

1. On the **Parameters** tab, click **New Parameter** in the toolbar.
2. In the **New Parameter** dialog, choose the **Parameter** card.
3. Fill in the form (see the table below).
4. Click **Create Parameter**.

The parameter appears in the library under its category.

| Field | Required | Notes |
| --- | --- | --- |
| **Name** | Yes | Must start with a letter or underscore. Can contain letters, numbers and underscores. No spaces. Up to 100 characters. |
| **Type** | Yes | Number, Text or Date. Can't be changed after creation. |
| **Value** | Yes | Must match the type. Dates use a date picker and are stored as YYYY-MM-DD. |
| **Category** | No | Assign to an existing category, or leave in **General**. Under "More options". |
| **Description** | No | Shown in the library and in the parameter picker. Under "More options". |

Every parameter created from this dialog is Project-scoped, so there's no Scope field. Names must be unique within their scope: you can't have two project-scoped parameters with the same name. See [Project and workspace scope](#project-and-workspace-scope).

## Create a Snippet

1. On the **Parameters** tab, click **New Parameter** and choose the **Snippet** card.
2. Set the **Name**. The rules are the same as for parameters.
3. Set the **Value**: the reusable SQL code. There's no language selector; snippets are always SQL. Type `/param` in the field to reference a parameter.
4. Optionally set **Category** and **Description** (under "More options").
5. Click **Create Snippet**.

The snippet appears in the library and can be referenced with `{{name}}`.

Snippet code can't reference other snippets. Saving fails with "Snippets cannot reference other snippets" if the code contains another snippet reference in double braces. Snippets can reference parameters, for example `{Max_Units}`.

## Edit a Parameter or Snippet

Click any item in the library to open its detail panel, then click **Edit**. You can also click the edit icon that appears when you hover over a row.

![Parameter detail panel for is_transaction with Edit and duplicate buttons, Properties showing value, category, reference syntax, and scope, and an empty Uses section](https://mammoth.io/docs/images/20260418_190110_parameter-detail-panel1.webp)

You can update the value, description and category. The **Name** is read-only once the item exists ("Name can't be edited"), and the **Type** and **Scope** can't be changed.

When you save an edit:

- All pipelines that reference the item are flagged stale. The detail panel shows, for example, **Stale in 3 pipelines** with a **Rerun** button.
- Stale banners with a **Rerun** button also appear in the SQL rule, Apply Filter and Data check panels that use the changed value.
- The change is recorded in the item's history in the detail panel.

## See which pipelines use a Parameter

Every parameter's detail panel has a **Uses** section listing each pipeline that references it, as a path of project, dataset and View. It shows exactly what a change will affect. Snippets show the same.

![Parameter detail panel for Pending_units with Uses 1, listing the path Marketing / Store Transaction / View 1](https://mammoth.io/docs/images/20260418_190154_parameter-uses-panel1.webp)

## Use a Parameter in a filter condition

You need a parameter that already exists. When you add a condition to a filter in **Builder** mode, the small chip in front of the value reads **Val** by default.

1. Open a pipeline and add or edit a filter condition.
2. Click the **Val** chip in front of the value and select **Parameter** ("Bind to a project parameter"). The chip changes to **#**.
3. In the picker, search for and select the parameter. The picker shows the parameters whose type matches the column. To create one without leaving the condition, use the **New Parameter** link in the picker.
4. Save the condition. To unbind the parameter later, click the X on its token.

The filter uses the parameter's current value each time the pipeline runs. Parameters can also be used as inputs in Data check. See [Filter rows](https://mammoth.io/docs/learn/clean-and-shape/filter-rows/).

![Add Condition dialog with Discount is less than Parameter chosen and a picker listing Pending_units, Number 100, with a New Parameter link](https://mammoth.io/docs/images/20260418_190227_add-condition-parameter-picker1.webp)

A Conditional Filter in **SQL** mode does not read parameters, and `{Max_Units}` text in it stays plain text. Use **Builder** mode for a parameter-driven filter.

## Where you can use a Parameter

| Step | How to add the parameter | Parameter types offered |
| --- | --- | --- |
| Conditional Filter, and any **Add Condition** built in **Builder** mode | **Val** chip > **Parameter** | The column's type |
| Label & Insert Values (**Enter a value**) | **Val** chip > **Parameter** | The result column's type |
| Find & Replace (**Find value**, **Replace with**) | **Val** chip > **Parameter** | Text |
| Show Top/Bottom Rows (row count) | **Val** chip > **Parameter** | Number |
| Obtain Large or Small Values (**Add a custom value to compare**) | **Val** chip > **Parameter** | Number |
| Math Function, **Formula** mode | **Insert Parameter** above the formula, or the autocomplete list | Number |
| Math Function, **SQL** mode | **Insert Parameter** above the **SQL Expression** editor | All. Text and Date parameters go in as `'{name}'` so they read as SQL strings. |

In Math Function, the parameter is written into the expression as `{name}`. Two errors can appear:

- "Parameter ... not found": the formula names a parameter that doesn't exist.
- "Only numeric parameters allowed, ... is not one": a Text or Date parameter is in a formula.

For the full formula syntax, see [Calculate with formulas](https://mammoth.io/docs/learn/clean-and-shape/formulas/).

## Use a Snippet in a SQL rule

In a SQL rule, click **Insert Snippet** and pick the snippet. Choose how to insert it:

| Option | What it inserts |
| --- | --- |
| **Reference** | `{{name}}`, which stays linked to the snippet. Later edits to the snippet reach the task. |
| **Paste value** | The snippet's current code as plain text, with no link to the snippet. |

```sql
SELECT customer_id, SUM(amount)
FROM transactions
WHERE {{standard_date_filter}}
GROUP BY 1
```

At run time, Mammoth substitutes the snippet's code in place of `{{standard_date_filter}}`. When the snippet code changes, its detail panel flags the pipelines that use it as stale. Use **Rerun** to apply the change.

## Rerun stale pipelines after a change

Saving a new value doesn't change any data straight away. Every pipeline that uses the item, in any of the steps above, is marked stale: its output may no longer reflect the current value. Mammoth does not rerun stale pipelines on its own; you start the rerun.

- Stale parameters are highlighted in the library, and the banner at the top offers **Rerun stale pipelines**.
- The detail panel shows a count such as **Stale in 3 pipelines** with a **Rerun** button.
- The SQL rule, Apply Filter and Data check panels show their own stale banner with **Rerun**.

A rerun reads the current value again and starts from the first task that uses the changed parameter, not from the beginning. Unchanged upstream tasks are not rerun.

## Group Parameters into categories

Parameters and snippets can be grouped into categories. By default, all items go into **General**.

- Category headings in the library have inline rename and delete icons.
- To add or manage categories, click **+ Manage** next to the category pills under **More options** when you create or edit an item.
- The **Manage categories** dialog lets you name categories and give them colours.

Deleting a category moves its items back to **General**. It does not delete the parameters or snippets.

## Duplicate a Parameter or Snippet

1. Open the detail panel (or hover over a row) and click the duplicate icon next to **Edit**.
2. The **Duplicate Parameter** or **Duplicate Snippet** dialog opens with `_copy` added to the name (for example, `Max_Units_copy`).
3. Change the name or value if you like.
4. Click **Create Duplicate**. Nothing is created until you click it.

If the `_copy` name is already taken, you get "Name already in use", so choose another name.

## Delete a Parameter or Snippet

Deleting a parameter or snippet is immediate and permanent. It has no Trash entry and no restore.

1. Open the detail panel and click the trash icon at the right of the header.
2. If no pipeline references the item, **Delete parameter** (or **Delete snippet**) asks "Are you sure you want to delete" followed by the name, for example `Max_Units`, and warns that this can't be undone.
3. Click **Delete** to confirm.

If a pipeline references the item, **Cannot delete parameter** (or **Cannot delete snippet**) says it "is used by pipelines and cannot be deleted". It lists each View with its task count and offers only **Close**. Remove the references first, then delete.

## Project and workspace scope

|  | Project scope | Workspace scope |
| --- | --- | --- |
| Visible in | This project only | All projects in the workspace |
| Reference syntax | `{name}` / `{{name}}` | Same syntax |
| Name uniqueness | Unique within this project | Unique across the workspace |
| Best for | Dataset-specific thresholds, View-specific logic | Shared standards, such as fiscal year start or company-wide thresholds |

The **New Parameter** dialog always creates a Project-scoped item; there is no Scope selector. Workspace-scoped parameters and snippets can exist in your workspace (for example, created through the API). Once they exist, you see and reference them like any other. A project-scoped `Threshold` and a workspace-scoped `Threshold` can coexist.

Scope can't be changed after an item is created.

## See the history of a Parameter

Every parameter and snippet keeps a history of changes in its detail panel. Each entry shows how long ago the change happened, with the old value struck through, followed by the new value. Use it to trace why a downstream dataset changed back to a specific edit.

## Limits

| Limit | Value |
| --- | --- |
| Name | Up to 100 characters; starts with a letter or underscore; letters, numbers and underscores only |
| Types | Number, Text, Date (parameters); SQL (snippets) |
| Snippets in snippets | Not allowed |

## Troubleshooting

| Symptom | Cause | Fix |
| --- | --- | --- |
| **New Parameter** is disabled: "Your role doesn't have permission to perform this action" | You are a Project Viewer. | Ask a Project Admin for the Editor role, or to make the change. |
| **Cannot delete parameter** | Pipelines still use it. | Remove the references in the listed Views, then delete. |
| "Snippets cannot reference other snippets" | The snippet code has another `{{...}}` reference. | Paste the other snippet's code instead, or use a parameter. |
| "Name already in use" | The duplicate's name exists. | Choose another name. |
| `{Max_Units}` stays as text in a filter | The Conditional Filter is in **SQL** mode. | Switch to **Builder** mode and bind the value with **Val** > **Parameter**. |
| "Only numeric parameters allowed, ... is not one" | A Text or Date parameter is in a Formula-mode Math Function. | Use a Number parameter, or switch to **SQL** mode. |
| Data didn't change after you edited a value | Mammoth doesn't rerun stale pipelines on its own. | Click **Rerun** or **Rerun stale pipelines**. |

## Related

- [Filter rows](https://mammoth.io/docs/learn/clean-and-shape/filter-rows/): build the conditions parameters plug into.
- [Calculate with formulas](https://mammoth.io/docs/learn/clean-and-shape/formulas/): Math Function and formula syntax.
- [Write SQL with AI](https://mammoth.io/docs/learn/clean-and-shape/sql-with-ai/): SQL rules where snippets go.
- [Find your way around the Data Library](https://mammoth.io/docs/learn/organise/data-library/): the tab bar that holds **Parameters**.
- [Get things back from Trash](https://mammoth.io/docs/learn/organise/trash/): what Trash covers, and why parameters aren't in it.

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Source: https://mammoth.io/docs/learn/organise/parameters-and-snippets.md · Updated: 2026-11-08