---
description: Using template variables with MySQL in Grafana
keywords:
  - grafana
  - mysql
  - templates
  - variables
  - queries
labels:
  products:
    - cloud
    - enterprise
    - oss
menuTitle: Template variables
title: MySQL template variables
weight: 300
---

# MySQL template variables

Instead of hard-coding details such as server, application, and sensor names in metric queries, you can use variables.
Grafana displays these variables in drop-down select boxes at the top of the dashboard to help you change the data displayed in your dashboard.
Grafana refers to such variables as **template variables**.

For an introduction to templating and template variables, refer to [Templating](https://grafana.com/docs/grafana/<GRAFANA_VERSION>/dashboards/variables/) and [Add and manage variables](https://grafana.com/docs/grafana/<GRAFANA_VERSION>/dashboards/variables/add-template-variables/).

## Query variable

A query variable in Grafana dynamically retrieves values from your data source using a query. With a query variable, you can write a SQL query that returns values such as measurement names, key names, or key values that are shown in a drop-down select box.

For example, the following query returns all values from the `hostname` column:

```sql
SELECT hostname FROM my_host
```

A query can return multiple columns, and Grafana automatically generates a list using the values from those columns. For example, the following query returns values from both the `hostname` and `hostname2` columns, which are included in the variable's drop-down list.

```sql
SELECT my_host.hostname, my_other_host.hostname2 FROM my_host JOIN my_other_host ON my_host.city = my_other_host.city
```

To use time range dependent macros like `$__timeFilter(column)` in your query, you must set the template variable's refresh mode to **On Time Range Change**.

```sql
SELECT event_name FROM event_log WHERE $__timeFilter(time_column)
```

### Key/value variables

You can create a key/value variable using a query that returns two columns named `__text` and `__value`.

- The `__text` column defines the label shown in the drop-down.
- The `__value` column defines the value passed to panel queries.

This is useful when you want to display a user-friendly label (like a hostname) but use a different underlying value (like an ID).

Note that the values in the `__text` column should be unique. If there are duplicates, Grafana uses only the first matching entry.

```sql
SELECT hostname AS __text, id AS __value FROM my_host
```

### Nested variables

You can create nested variables, where one variable depends on the value of another. For example, if you have a variable named `region`, you can configure a `hosts` variable to only show hosts from the selected region. If `region` is a multi-value variable, use the `IN` operator instead of `=` to match against multiple selected values.

```sql
SELECT hostname FROM my_host WHERE region IN($region)
```

### Filter results with `__searchFilter`

Using `__searchFilter` in the query field allows the query results to be filtered based on the user's input in the drop-down selection box. If you don't enter anything, the default value for `__searchFilter` is `%`.

Note that you must enclose the `__searchFilter` expression in quotes as Grafana doesn't add them automatically.

The following example demonstrates how to use `__searchFilter` in the query field to enable real-time searching for `hostname` as the user types in the drop-down selection box.

```sql
SELECT hostname FROM my_host WHERE hostname LIKE '$__searchFilter'
```

## Use variables in queries

Grafana automatically quotes template variable values only when the template variable is a `multi-value`.

When using a multi-value variable, use the `IN` comparison operator instead of `=` to match against multiple values.

Grafana supports two syntaxes for using variables in queries:

- **`$<varname>` syntax**

Example with a template variable named `hostname`:

```sql
SELECT
  UNIX_TIMESTAMP(atimestamp) as time,
  aint as value,
  avarchar as metric
FROM my_table
WHERE $__timeFilter(atimestamp) and hostname in($hostname)
ORDER BY atimestamp ASC
```

- **`[[varname]]` syntax**

Example with a template variable named `hostname`:

```sql
SELECT
  UNIX_TIMESTAMP(atimestamp) as time,
  aint as value,
  avarchar as metric
FROM my_table
WHERE $__timeFilter(atimestamp) and hostname in([[hostname]])
ORDER BY atimestamp ASC
```

### Disable quoting for multi-value variables

By default, Grafana formats multi-value variables as a quoted, comma-separated string. For example, if `server01` and `server02` are selected, the result will be `'server01'`, `'server02'`. To disable quoting, use the `csv` formatting option for variables:

```text
${servers:csv}
```

This outputs the values as an unquoted comma-separated list.

Refer to [Advanced variable format options](https://grafana.com/docs/grafana/<GRAFANA_VERSION>/dashboards/variables/variable-syntax/#advanced-variable-format-options) for additional information.
