---
title: Regular expressions
description: Use regular expressions to match patterns in your data.
url: https://docs.influxdata.com/influxdb/v2/query-data/influxql/explore-data/regular-expressions/
estimated_tokens: 4801
product: InfluxDB OSS v2
version: v2
---

# Regular expressions

This page documents an earlier version of InfluxDB OSS. [InfluxDB 3 Core](/influxdb3/core/) is the latest stable version.

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For more information, see [Token hashing](/influxdb/v2/admin/tokens/#token-hashing).

InfluxQL supports using regular expressions when specifying:

-   [field keys](/influxdb/v2/reference/glossary/#field-key) and [tag keys](/influxdb/v2/reference/glossary/#tag-key) in the [`SELECT` clause](/influxdb/v2/query-data/influxql/explore-data/select/).
-   [measurements](/influxdb/v2/reference/glossary/#measurement) in the [`FROM` clause](/influxdb/v2/query-data/influxql/explore-data/select/#from-clause).
-   [tag values](/influxdb/v2/reference/glossary/#tag-value) and string [field values](/influxdb/v2/reference/glossary/#field-value) in the [`WHERE` clause](/influxdb/v2/query-data/influxql/explore-data/where/).
-   [tag keys](/influxdb/v2/reference/glossary/#tag-key) in the [`GROUP BY` clause](/influxdb/v2/query-data/influxql/explore-data/group-by/)

Regular expressions in InfluxQL only support string comparisons and can only evaluate [fields](/influxdb/v2/reference/glossary/#field) with string values.

**Note:** Regular expression comparisons are more computationally intensive than exact string comparisons. Queries with regular expressions are not as performant as those without.

-   [Syntax](#syntax)
-   [Examples](#examples)

## Syntax

```sql
SELECT /<regular_expression_field_key>/ FROM /<regular_expression_measurement>/ WHERE [<tag_key> <operator> /<regular_expression_tag_value>/ | <field_key> <operator> /<regular_expression_field_value>/] GROUP BY /<regular_expression_tag_key>/
```

Regular expressions are surrounded by `/` characters and use the [Go regular expression syntax](http://golang.org/pkg/regexp/syntax/).

## Supported operators

`=~`: matches against `!~`: doesn’t match against

### Examples

[](#use-a-regular-expression-to-specify-field-keys-and-tag-keys-in-the-select-clause)

Use a regular expression to specify field keys and tag keys in the SELECT clause

```sql
SELECT /l/ FROM "h2o_feet" LIMIT 1
```

Output:

Name: h2o\_feet

| time | level description | location | water_level |
| --- | --- | --- | --- |
| 2019-08-17T00:00:00Z | below 3 feet | santa_monica | 2.0640000000 |

The query selects all field keys and tag keys that include an `l`. Note that the regular expression in the `SELECT` clause must match at least one field key in order to return results for a tag key that matches the regular expression.

Currently, there is no syntax to distinguish between regular expressions for field keys and regular expressions for tag keys in the `SELECT` clause. The syntax `/<regular_expression>/::[field | tag]` is not supported.

[](#use-a-regular-expression-to-specify-field-keys-and-tag-keys-in-function-arguments)

Use a regular expression to specify field keys and tag keys in function arguments

```sql
SELECT MAX(/_level/) FROM "h2o_feet" LIMIT 1
```

Output:

Name: h2o\_feet

| time | max_water_level |
| --- | --- |
| 2019-08-28T07:24:00Z | 9.964 |

This query uses the InfluxQL [`MAX()` selector function](/influxdb/v2/query-data/influxql/functions/selectors/#max) to find the greatest field value out of all field keys that match the regular expression.

[](#use-a-regular-expression-to-specify-measurements-in-the-from-clause)

Use a regular expression to specify measurements in the FROM clause

```sql
SELECT MEAN("degrees") FROM /temperature/
```

Output:

Name: average\_temperature

| time | mean |
| --- | --- |
| 1970-01-01T00:00:00Z | 79.9847293223 |

Name: h2o\_feet

| time | mean |
| --- | --- |
| 1970-01-01T00:00:00Z | 64.9980273540 |

This query uses the InfluxQL [MEAN() function](/influxdb/v2/query-data/influxql/functions/aggregates/#mean) to calculate the average `degrees` for every [measurement](/influxdb/v2/reference/glossary/#measurement) in the \[NOAA sample data\] that contains the word `temperature`.

[](#use-a-regular-expression-to-specify-tag-values-in-the-where-clause)

Use a regular expression to specify tag values in the WHERE clause

```sql
SELECT MEAN(water_level) FROM "h2o_feet" WHERE "location" =~ /[m]/ AND "water_level" > 3
```

Output:

Name: h2o\_feet

| time | mean |
| --- | --- |
| 1970-01-01T00:00:00Z | 4.4710766395 |

This query uses the InfluxQL [MEAN() function](/influxdb/v2/query-data/influxql/functions/aggregates/#mean) to calculate the average `water_level` where the [tag value](/influxdb/v2/reference/glossary/#measurement) of `location` includes an `m` and `water_level` is greater than three.

[](#use-a-regular-expression-to-specify-a-tag-with-no-value-in-the-where-clause)

Use a regular expression to specify a tag with no value in the WHERE clause

```sql
SELECT * FROM "h2o_feet" WHERE "location" !~ /./
>
```

The query selects all data from the `h2o_feet` measurement where the `location` [tag](/influxdb/v2/reference/glossary/#tag) has no value. Every data [point](/influxdb/v2/reference/glossary/#point) in the [NOAA water sample data](/influxdb/v2/reference/sample-data/#noaa-water-sample-data) has a tag value for `location`. It’s possible to perform this same query without a regular expression. See the [Frequently Asked Questions](/influxdb/v2/reference/faq/#how-do-i-query-data-by-a-tag-with-a-null-value) document for more information.

[](#use-a-regular-expression-to-specify-a-tag-with-a-value-in-the-where-clause)

Use a regular expression to specify a tag with a value in the WHERE clause

```sql
SELECT MEAN("water_level") FROM "h2o_feet" WHERE "location" =~ /./
```

Output:

Name: h2o\_feet

| time | mean |
| --- | --- |
| 1970-01-01T00:00:00Z | 4.4418434585 |

This query uses the InfluxQL [MEAN() function](/influxdb/v2/query-data/influxql/functions/aggregates/#mean) to calculate the average `water_level` across all data with a tag value for `location`.

[](#use-a-regular-expression-to-specify-a-field-value-in-the-where-clause)

Use a regular expression to specify a field value in the WHERE clause

```sql
SELECT MEAN("water_level") FROM "h2o_feet" WHERE "location" = 'santa_monica' AND "level description" =~ /between/
```

Output:

Name: h2o\_feet

| time | mean |
| --- | --- |
| 1970-01-01T00:00:00Z | 4.4713666916 |

This query uses the InfluxQL [MEAN() function](/influxdb/v2/query-data/influxql/functions/aggregates/#mean) to calculate the average `water_level` for all data where the field value of `level description` includes the word `between`.

[](#use-a-regular-expression-to-specify-tag-keys-in-the-group-by-clause)

Use a regular expression to specify tag keys in the GROUP BY clause

```sql
SELECT FIRST("index") FROM "h2o_quality" GROUP BY /l/
```

Output:

name: h2o\_quality  
tags: location=coyote\_creek

| time | mean |
| --- | --- |
| 2019-08-17T00:00:00Z | 41.0000000000 |

name: h2o\_quality  
tags: location=santa\_monica

| time | mean |
| --- | --- |
| 2019-08-17T00:00:00Z | 99.0000000000 |

This query uses the InfluxQL [FIRST() function](/influxdb/v2/query-data/influxql/functions/selectors/#first)

to select the first value of `index` for every tag that includes the letter `l` in its tag key.