---
title: Regular expressions
description: Use regular expressions to match patterns in your data.
url: https://docs.influxdata.com/influxdb3/cloud-dedicated/reference/influxql/regular-expressions/
estimated_tokens: 4474
product: InfluxDB Cloud Dedicated
version: cloud-dedicated
---

# Regular expressions

Regular expressions are a sequence of characters used to identify patterns in identifiers and string values. InfluxQL supports regular expressions in the following operations:

-   Identifying **fields** and **tags** to query in the [`SELECT` clause](/influxdb3/cloud-dedicated/reference/influxql/select/).
-   Identifying **measurements** to query in the [`FROM` clause](/influxdb3/cloud-dedicated/reference/influxql/select/#from-clause).
-   Testing **tag values** and **string field values** in the [`WHERE` clause](/influxdb3/cloud-dedicated/reference/influxql/where/).
-   Identifying **tag keys** to group by in the [`GROUP BY` clause](/influxdb3/cloud-dedicated/reference/influxql/group-by/)

#### Query performance

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

## Regular expression syntax

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

```sql
/regular_expression/
```

### Regular expression flags

Regular expression flags modify the pattern-matching behavior of the expression. InfluxQL supports the following regular expression flags:

| Flag | Description |
| --- | --- |
| i | case-insensitive |
| m | multi-line mode: ^ and $ match begin/end line in addition to begin/end text |
| s | let . match \n |
| U | ungreedy: swap meaning of x* and x*?, x+ and x+?, etc. |

Include regular expression flags at the beginning of your regular expression pattern enclosed in parentheses (`()`) and preceded by a question mark (`?`).

```sql
/(?iU)foo*/
```

## Regular expression operators

InfluxQL provides the following regular expression operators that test if a string operand matches a regular expression:

-   `=~`: Returns true if the string matches the regular expression
-   `!~`: Returns true if the string does not match the regular expression

InfluxQL regular expression operators are used to test string column values in the [`WHERE` clause](/influxdb3/cloud-dedicated/reference/influxql/where/).

## Regular expression examples

The examples below use the following sample data sets:

-   [NOAA Bay Area weather data](/influxdb3/cloud-dedicated/reference/sample-data/#noaa-bay-area-weather-data)
-   [Get started home sensor data](/influxdb3/cloud-dedicated/reference/sample-data/#home-sensor-data)

[](#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 /^t/ FROM weather
```

name: weather

| time | temp_avg | temp_max | temp_min |
| --- | --- | --- | --- |
| 2020-01-01T00:00:00Z | 52 | 66 | 44 |
| 2020-01-01T00:00:00Z | 53 | 59 | 47 |
| 2020-01-01T00:00:00Z | 50 | 57 | 44 |
| 2020-01-02T00:00:00Z | 54 | 61 | 49 |
| 2020-01-02T00:00:00Z | 51 | 60 | 44 |
| 2020-01-02T00:00:00Z | 53 | 66 | 42 |
| … | … | … | … |

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

Use a regular expression to specify measurements in the FROM clause

```sql
SELECT /^t/ FROM /^[hw]/
```

name: weather

| time | temp | temp_avg | temp_max | temp_min |
| --- | --- | --- | --- | --- |
| 2020-01-01T00:00:00Z |  | 52 | 66 | 44 |
| 2020-01-01T00:00:00Z |  | 53 | 59 | 47 |
| 2020-01-01T00:00:00Z |  | 50 | 57 | 44 |
| 2020-01-02T00:00:00Z |  | 54 | 61 | 49 |
| 2020-01-02T00:00:00Z |  | 51 | 60 | 44 |
| 2020-01-02T00:00:00Z |  | 53 | 66 | 42 |
| … | … | … | … | … |

[](#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 * FROM weather WHERE location !~ /^[S]/
```

name: weather

| time | location | precip | temp_avg | temp_max | temp_min | wind_avg |
| --- | --- | --- | --- | --- | --- | --- |
| 2020-01-01T00:00:00Z | Concord | 0 | 52 | 66 | 44 | 3.13 |
| 2020-01-01T00:00:00Z | Hayward | 0 | 50 | 57 | 44 | 2.24 |
| 2020-01-02T00:00:00Z | Concord | 0 | 53 | 66 | 42 | 3.13 |
| 2020-01-02T00:00:00Z | Hayward | 0 | 51 | 60 | 44 | 3.8 |
| 2020-01-03T00:00:00Z | Concord | 0 | 49 | 60 | 38 | 2.68 |
| 2020-01-03T00:00:00Z | Hayward | 0 | 50 | 62 | 41 | 3.13 |
| … | … | … | … | … | … | … |

[](#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 home, weather WHERE location !~ /./
```

name: weather

| time | co | hum | location | precip | room | temp | temp_avg | temp_max | temp_min | wind_avg |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| 2022-01-01T08:00:00Z | 0 | 35.9 |  |  | Kitchen | 21 |  |  |  |  |
| 2022-01-01T08:00:00Z | 0 | 35.9 |  |  | Living Room | 21.1 |  |  |  |  |
| 2022-01-01T09:00:00Z | 0 | 36.2 |  |  | Kitchen | 23 |  |  |  |  |
| 2022-01-01T09:00:00Z | 0 | 35.9 |  |  | Living Room | 21.4 |  |  |  |  |
| 2022-01-01T10:00:00Z | 0 | 36.1 |  |  | Kitchen | 22.7 |  |  |  |  |
| 2022-01-01T10:00:00Z | 0 | 36 |  |  | Living Room | 21.8 |  |  |  |  |
| … | … | … | … | … | … | … | … | … | … | … |

[](#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 MAX(precip) FROM weather GROUP BY /^l/
```

name: weather  
tags: location=Concord

| time | max |
| --- | --- |
| 2021-10-24T00:00:00Z | 4.53 |

name: weather  
tags: location=Hayward

| time | max |
| --- | --- |
| 2022-12-31T00:00:00Z | 4.34 |

name: weather  
tags: location=San Francisco

| time | max |
| --- | --- |
| 2021-10-24T00:00:00Z | 4.02 |