> ## Documentation Index
> Fetch the complete documentation index at: https://honeydew.ai/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# Parameters

## Introduction to Parameters

Parameters can be used to create global constants.

A parameter can be used with a \$ sign, like `$status` in this parameterized filtered metric:

```sql theme={null}
orders.count FILTER (WHERE orders.status = $status)
```

Parameters are defined either per workspace, per domain, or per dynamic dataset.
The definition includes parameter name and default value.

Parameter values can be overridden based on the following hierarchy:

1. Global value (per workspace)
2. In a [domain](/docs/domains)
3. In a query (when using the [SQL interface](/docs/integration/sql-interface)) or in a [dynamic dataset](/docs/dynamic-datasets)

<Tip>
  Using parameterized semantics in a dynamic dataset deployed as a VIEW allows to create parameterized views
</Tip>

## Parameterized Dynamic Datasets

Dynamic datasets can include calculations with parameters.

The value of the parameter when in a user query is by this order:

1. Value set in real-time by user with a `SET` command.
2. Default value set in the dynamic dataset
3. Default value set in the domain
4. Default value set in the workspace

A dynamic dataset parameter default value can override a domain parameter or a workspace parameter of the same name.

### Deploying to VIEWs

When a dynamic dataset is deployed as a Snowflake `VIEW`, parameters can be set using the Snowflake `SET` statement:

```sql theme={null}
-- run in Snowflake, on a view that uses the $status parameter

SET status='O';
SELECT * FROM [Honeydew Dataset Deployed View];
```

### Deploying to TABLEs

When a dynamic dataset is deployed as a Snowflake TABLE (regular or dynamic) the default values of parameters are used, as set in the dynamic dataset configuration.

## Using parameters within a SQL interface connection

If there is a SQL interface table or domain called `world`, and a parameter called `param`, set it as:

```sql theme={null}
SELECT ...
FROM (
  SELECT *, 12 as "$param" from world
)
```

The statement above selects from `world` with 12 as the value of parameter `param`.

## Dynamic parameters using UDFs

Parameter values can be computed using user defined functions (UDF) in Snowflake, by using the UDF in the parameter expression:

```sql theme={null}
SELECT ...
FROM (
  SELECT *, my_udf(12) as "$param" from world
)
```

The statement above selects from `world` with parameter `param` set to the result of UDF `my_udf(12)`.

This approach allows complex computation of parameters, using other functions or data in Snowflake.

For example, a user parameter can be used to extract value from a lookup table:

```sql theme={null}
-- A user defined function that maps keys to value
CREATE OR REPLACE FUNCTION my_udf (key number)
RETURNS varchar
AS 'select value from lookup_table where key = lookup_table.key limit 1';
```

## YAML Schema

Each parameter is defined by a YAML file in Git, which also tracks and preserves the full history of every change.

The schema for parameter is:

```yaml theme={null}
type: parameter
name: <name>
display_name: <display name>
owner: <owner>
description: |-
  <description>
labels: [label1, label2, ...]
tags:
  - key: <key>
    value: <value>
    source: <snowflake/databricks/bigquery/honeydew/other>
  - ...
folder: <folder>
hidden: <True/False/Yes/No>
value: |-
  <value statement>
```

Fields:

* `name`: Name of parameter (global)
* `value`: SQL constant expression (i.e. a number or a string)
* `display_name`, `owner`, `description`, `labels`, `tags`, `folder`, `hidden`: Metadata