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

# Metric Filter - Variable

> Variable Filter in Metric Filter: Quick Instruction Manual

> Master dynamic filtering in Databrain with Variable Filters—your key to building flexible,
> interactive metrics. This guide demonstrates how to transform static SQL queries into dynamic
> data explorations, empowering users to filter complex datasets effortlessly.

### Using Variable Filter in Metric Filter with Custom SQL

#### Creating a Metric Filter with Variable Filter:

1. **Create Metric Filter**
2. In the **“Apply On”** section, choose **"Variable Filter"**.
3. **Assign Variable Name**:
   * Assign a variable name, for example, `{{value}}`.
   * Copy the variable `{{value}}` for use in your custom SQL query.

<Frame>
  <img src="https://mintcdn.com/databrainlabs-bef6850a/oJW5seGO2mMUK4Ch/images/guides/metric-filter-variable.png?fit=max&auto=format&n=oJW5seGO2mMUK4Ch&q=85&s=641fe458b9ff8385d67e5137560136ad" width="1526" height="1178" data-path="images/guides/metric-filter-variable.png" />
</Frame>

### Example Use Case: Dynamic Country Population Analysis

#### Scenario:

Imagine a dashboard where analysts can quickly filter population data for different countries—without needing to modify the underlying SQL query every time.

#### Purpose of Variable Filter:

**Where to use the variable:**\
Filter variables (e.g. `{{value}}`, `{{global_value}}`) are **only valid in the WHERE clause** of your metric's SQL (and in the filter's Apply on logic). Do **not** use them in SELECT, FROM, or GROUP BY—doing so will trigger: **Error: Filter or Client variables detected in the query.** There is no built-in way to "inspect" or display the current filter value in a metric.

#### Example Custom SQL Query with Variable Filter:

* **Custom SQL you write:**

```sql theme={"dark"}
SELECT
  "country" AS "country",
  "population" AS "population"
FROM
  "public"."table"
```

* **Custom SQL added with Variable Filter:**

```sql theme={"dark"}
SELECT
  "country" AS "country",
  "population" AS "population"
FROM
  "public"."table"
WHERE
  "country" = {{value}}
```

Then the Generated SQL we generate would look like this:

* **Resulting SQL:**

```sql theme={"dark"}
SELECT
  "country" AS "country",
  "population" AS "population"
FROM
(
  SELECT
    "country" AS "country",
    "population" AS "population"
  FROM
    "public"."table"
  WHERE
    "country" = {{value}}
) AS "dbn_sql_table"
```

***

**Working:**

* The initial SQL query retrieves all country population data.
* The Variable Filter dynamically adds a condition using `{{value}}`.
* When a user selects a country from the dashboard, the filter updates the query.
* The results are filtered instantly based on the selected country.