# How Do I Write a Prometheus Query That Returns the Value of a Label?

To write a Prometheus query that returns the value of a specific label, you need to use the basic syntax for querying metrics and utilize the appropriate label matchers. Here’s how to construct a query to extract the value of a label from a specific metric.

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### Basic Query Structure

The general structure for querying metrics in Prometheus is:

```
metric_name{label_name="label_value"}
```

### Example Scenario

Let’s say you have a metric called `http_requests_total`, which counts the total number of HTTP requests and has labels such as `method`, `status`, and `instance`. Here’s how you can query to return values based on these labels.

### Step 1: Query a Metric with Specific Labels

To get the total number of HTTP requests for a specific method (e.g., `GET`), you would write:

```
http_requests_total{method="GET"}
```

This query returns the total number of `GET` requests, including all instances of the metric. If you want to see this value aggregated by status code, you could use:

```
sum(http_requests_total{method="GET"}) by (status)
```

This returns the sum of `GET` requests grouped by their status codes.

### Step 2: Return Values of All Unique Labels

If you want to return all the unique values of a specific label (e.g., `method`) from the `http_requests_total` metric, you can use the `label_values` function in conjunction with the Prometheus UI or Grafana.

For example, to get unique methods used in the requests:

```
label_values(http_requests_total, method)
```

### Step 3: Using the `group` Function

To focus specifically on extracting label values, you can also use the `group` function to return a list of unique label values. This is particularly useful when visualizing metrics or generating reports.

For example, if you want to see the unique values of the `instance` label:

```
count(http_requests_total) by (instance)
```

This counts the number of occurrences of `http_requests_total` for each unique `instance` label.

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