---
title: Explore your schema using InfluxQL
description: Learn to use InfluxQL to explore the schema of your time series data.
url: https://docs.influxdata.com/influxdb/v2/query-data/influxql/explore-schema/
estimated_tokens: 10062
product: InfluxDB OSS v2
version: v2
---

# Explore your schema using InfluxQL

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

#### API token hashing is enabled by default in InfluxDB OSS 2.9.0

Stronger token security: tokens are stored as hashes on disk, so a copy of the database file doesn’t expose usable tokens. Existing tokens are hashed on first startup and the original strings can’t be recovered afterward — **capture any plaintext tokens you still need before you upgrade**.

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

Use InfluxQL to explore the schema of your time series data. Use the following InfluxQL commands to explore your schema:

-   [SHOW SERIES](#show-series)
-   [SHOW MEASUREMENTS](#show-measurements)
-   [SHOW TAG KEYS](#show-tag-keys)
-   [SHOW TAG VALUES](#show-tag-values)
-   [SHOW FIELD KEYS](#show-field-keys)
-   [SHOW FIELD KEY CARDINALITY](#show-field-key-cardinality)
-   [SHOW TAG KEY CARDINALITY](#show-tag-key-cardinality)

Command examples use the [NOAA water sample data](/influxdb/v2/reference/sample-data/#noaa-water-sample-data).

## SHOW SERIES

Return a list of [series](/influxdb/v2/reference/glossary/#series) for the specified [database](/influxdb/v2/reference/glossary/#database).

### Syntax

```sql
SHOW SERIES [ON <database_name>] [FROM_clause] [WHERE <tag_key> <operator> [ '<tag_value>' | <regular_expression>]] [LIMIT_clause] [OFFSET_clause]
```

-   `ON <database_name>` is optional. If the query does not include `ON <database_name>`, you must specify the database with the `db` query string parameter in the [InfluxDB API](/influxdb/v2/reference/api/influxdb-1x/) request.
    
-   `FROM`, `WHERE`, `LIMIT`, and `OFFSET` clauses are optional.
    
-   The `WHERE` clause in `SHOW SERIES` supports tag comparisons but not field comparisons.
    
    **Supported operators in the `WHERE` clause**:
    
    -   `=`: equal to
    -   `<>`: not equal to
    -   `!=`: not equal to
    -   `=~`: matches against
    -   `!~`: doesn’t match against

See [Explore data using InfluxQL](/influxdb/v2/query-data/influxql/explore-data/) for documentation on the [`FROM` clause](/influxdb/v2/query-data/influxql/explore-data/select/#from-clause), [`LIMIT` clause](/influxdb/v2/query-data/influxql/explore-data/limit-and-slimit/), [`OFFSET` clause](/influxdb/v2/query-data/influxql/explore-data/offset-and-soffset/), and [Regular Expressions](/influxdb/v2/query-data/influxql/explore-data/regular-expressions/).

### Examples

#### Run SHOW SERIES with the ON clause

```sql
SHOW SERIES ON noaa
```

**Output:**

The query returns all series in the `noaa` database. The query’s output is similar to the [line protocol](/influxdb/v2/reference/syntax/line-protocol/) format. Everything before the first comma is the [measurement](/influxdb/v2/reference/glossary/#measurement) name. Everything after the first comma is either a [tag key](/influxdb/v2/reference/glossary/#tag-key) or a [tag value](/influxdb/v2/reference/glossary/#tag-value). The `noaa` database has 5 different measurements and 13 different series.

| key |
| --- |
| average_temperature,location=coyote_creek |
| average_temperature,location=santa_monica |
| h2o_feet,location=coyote_creek |
| h2o_feet,location=santa_monica |
| h2o_pH,location=coyote_creek |
| h2o_pH,location=santa_monica |
| h2o_quality,location=coyote_creek,randtag=1 |
| h2o_quality,location=coyote_creek,randtag=2 |
| h2o_quality,location=coyote_creek,randtag=3 |
| h2o_quality,location=santa_monica,randtag=1 |
| h2o_quality,location=santa_monica,randtag=2 |
| h2o_quality,location=santa_monica,randtag=3 |
| h2o_temperature,location=coyote_creek |

#### Run SHOW SERIES with several clauses

```sql
SHOW SERIES ON noaa FROM "h2o_quality" WHERE "location" = 'coyote_creek' LIMIT 2
```

**Output:**

The query returns all series in the `noaa` database that are associated with the `h2o_quality` measurement and the tag `location = coyote_creek`. The `LIMIT` clause limits the number of series returned to two.

| key |
| --- |
| h2o_quality,location=coyote_creek,randtag=1 |
| h2o_quality,location=coyote_creek,randtag=2 |

## SHOW MEASUREMENTS

Returns a list of [measurements](/influxdb/v2/reference/glossary/#measurement) for the specified [database](/influxdb/v2/reference/glossary/#database).

### Syntax

```sql
SHOW MEASUREMENTS [ON <database_name>] [WITH MEASUREMENT <operator> ['<measurement_name>' | <regular_expression>]] [WHERE <tag_key> <operator> ['<tag_value>' | <regular_expression>]] [LIMIT_clause] [OFFSET_clause]
```

-   `ON <database_name>` is optional. If the query does not include `ON <database_name>`, you must specify the database with the `db` query string parameter in the [InfluxDB API](/influxdb/v2/reference/api/influxdb-1x/) request.
    
-   The `WITH`, `WHERE`, `LIMIT` and `OFFSET` clauses are optional.
    
-   The `WHERE` in `SHOW MEASUREMENTS` supports tag comparisons, but not field comparisons.
    
    **Supported operators in the `WHERE` clause:**
    
    -   `=` : equal to
    -   `<>`: not equal to
    -   `!=`: not equal to
    -   `=~`: matches against
    -   `!~`: doesn’t match against

See [Explore data using InfluxQL](/influxdb/v2/query-data/influxql/explore-data/) for documentation on the [`FROM` clause](/influxdb/v2/query-data/influxql/explore-data/select/#from-clause), [`LIMIT` clause](/influxdb/v2/query-data/influxql/explore-data/limit-and-slimit/), [`OFFSET` clause](/influxdb/v2/query-data/influxql/explore-data/offset-and-soffset/), and [Regular Expressions](/influxdb/v2/query-data/influxql/explore-data/regular-expressions/).

### Examples

#### Run SHOW MEASUREMENTS with the ON clause

```sql
SHOW MEASUREMENTS ON noaa
```

**Output:**

The query returns the list of measurements in the `noaa` database. The database has five measurements: `average_temperature`, `h2o_feet`, `h2o_pH`, `h2o_quality`, and `h2o_temperature`.

| name |
| --- |
| average_temperature |
| h2o_feet |
| h2o_pH |
| h2o_quality |
| h2o_temperature |

#### Run SHOW MEASUREMENTS with several clauses (i)

```sql
SHOW MEASUREMENTS ON noaa WITH MEASUREMENT =~ /h2o.*/ LIMIT 2 OFFSET 1
```

**Output:**

The query returns the measurements in the `noaa` database that start with `h2o`. The `LIMIT` and `OFFSET` clauses limit the number of measurement names returned to two and offset the results by one, skipping the `h2o_feet` measurement.

| name |
| --- |
| h2o_pH |
| h2o_quality |

#### Run SHOW MEASUREMENTS with several clauses (ii)

```sql
SHOW MEASUREMENTS ON noaa WITH MEASUREMENT =~ /h2o.*/ WHERE "randtag"  =~ /\d/
```

The query returns all measurements in the `noaa` that start with `h2o` and have values for the tag key `randtag` that include an integer.

| name |
| --- |
| h2o_quality |

## SHOW TAG KEYS

Returns a list of [tag keys](/influxdb/v2/reference/glossary/#tag-key) associated with the specified [database](/influxdb/v2/reference/glossary/#database).

### Syntax

```sql
SHOW TAG KEYS [ON <database_name>] [FROM_clause] WITH KEY [ [<operator> "<tag_key>" | <regular_expression>] | [IN ("<tag_key1>","<tag_key2>")]] [WHERE <tag_key> <operator> ['<tag_value>' | <regular_expression>]] [LIMIT_clause] [OFFSET_clause]
```

-   `ON <database_name>` is optional. If the query does not include `ON <database_name>`, you must specify the database with `db` query string parameter in the [InfluxDB API](/influxdb/v2/reference/api/influxdb-1x/) request.
    
-   The `FROM` clause and the `WHERE` clause are optional.
    
-   The `WHERE` clause in `SHOW TAG KEYS` supports tag comparisons, but not field comparisons.
    
    **Supported operators in the `WHERE` clause:**
    
    -   `=` : equal to
    -   `<>`: not equal to
    -   `!=`: not equal to
    -   `=~`: matches against
    -   `!~`: doesn’t match against

See [Explore data using InfluxQL](/influxdb/v2/query-data/influxql/explore-data/) for documentation on the [`FROM` clause](/influxdb/v2/query-data/influxql/explore-data/select/#from-clause), [`LIMIT` clause](/influxdb/v2/query-data/influxql/explore-data/limit-and-slimit/), [`OFFSET` clause](/influxdb/v2/query-data/influxql/explore-data/offset-and-soffset/), and [Regular Expressions](/influxdb/v2/query-data/influxql/explore-data/regular-expressions/).

### Examples

#### Run SHOW TAG KEYS with the ON clause

```sql
SHOW TAG KEYS ON noaa
```

**Output:**

The query returns the list of tag keys in the `noaa` database. The output groups tag keys by measurement name; it shows that every measurement has the `location` tag key and that the `h2o_quality` measurement has an additional `randtag` tag key.

| name | tagKey |
| --- | --- |
| average_temperature | location |
| h2o_feet | location |
| h2o_pH | location |
| h2o_quality | location |
| h2o_quality | randtag |
| h2o_temperature | location |

#### Run SHOW TAG KEYS with several clauses

```sql
SHOW TAG KEYS ON noaa FROM "h2o_quality" LIMIT 1 OFFSET 1
```

**Output:**

The query returns tag keys from the `h2o_quality` measurement in the `noaa` database. The `LIMIT` and `OFFSET` clauses limit the number of tag keys returned to one and offsets the results by one.

| name | tagKey |
| --- | --- |
| h2o_quality | randtag |

#### Run SHOW TAG KEYS with a WITH KEY IN clause

```sql
SHOW TAG KEYS ON noaa WITH KEY IN ("location") 
```

**Output:**

| measurement | tagKey |
| --- | --- |
| average_temperature | location |
| h2o_feet | location |
| h2o_pH | location |
| h2o_quality | location |
| h2o_quality | randtag |
| h2o_temperature | location |

## SHOW TAG VALUES

Returns the list of [tag values](/influxdb/v2/reference/glossary/#tag-value) for the specified [tag key(s)](/influxdb/v2/reference/glossary/#tag-key) in the database.

### Syntax

```sql
SHOW TAG VALUES [ON <database_name>][FROM_clause] WITH KEY [ [<operator> "<tag_key>" | <regular_expression>] | [IN ("<tag_key1>","<tag_key2>")]] [WHERE <tag_key> <operator> ['<tag_value>' | <regular_expression>]] [LIMIT_clause] [OFFSET_clause]
```

-   `ON <database_name>` is optional. If the query does not include `ON <database_name>`, you must specify the database with the `db` query string parameter in the [InfluxDB API](/influxdb/v2/reference/api/influxdb-1x/) request.
    
-   The `WITH` clause is required. It supports specifying a single tag key, a regular expression, and multiple tag keys.
    
-   The `FROM`, `WHERE`, `LIMIT`, and `OFFSET` clauses are optional.
    
-   The `WHERE` clause in `SHOW TAG KEYS` supports tag comparisons, but not field comparisons.
    
    **Supported operators in the `WITH` and `WHERE` clauses:**
    
    -   `=` : equal to
    -   `<>`: not equal to
    -   `!=`: not equal to
    -   `=~`: matches against
    -   `!~`: doesn’t match against

See [Explore data using InfluxQL](/influxdb/v2/query-data/influxql/explore-data/) for documentation on the [`FROM` clause](/influxdb/v2/query-data/influxql/explore-data/select/#from-clause), [`LIMIT` clause](/influxdb/v2/query-data/influxql/explore-data/limit-and-slimit/), [`OFFSET` clause](/influxdb/v2/query-data/influxql/explore-data/offset-and-soffset/), and [Regular Expressions](/influxdb/v2/query-data/influxql/explore-data/regular-expressions/).

### Examples

#### Run SHOW TAG VALUES with the ON clause

```sql
SHOW TAG VALUES ON noaa WITH KEY = "randtag"
```

**Output:**

The query returns all tag values of the `randtag` tag key in the `noaa` database. `SHOW TAG VALUES` groups query results by measurement name.

name: h2o\_quality

| key | value |
| --- | --- |
| randtag | 1 |
| randtag | 2 |
| randtag | 3 |

#### Run a `SHOW TAG VALUES` query with several clauses

```sql
SHOW TAG VALUES ON noaa WITH KEY IN ("location","randtag") WHERE "randtag" =~ /./ LIMIT 3
```

**Output:**

The query returns the tag values of the tag keys `location` and `randtag` for all measurements in the `noaa` database where `randtag` has tag values. The `LIMIT` clause limits the number of tag values returned to three.

name: h2o\_quality

| key | value |
| --- | --- |
| location | coyote_creek |
| location | santa_monica |
| randtag | 1 |

## SHOW FIELD KEYS

Returns the [field keys](/influxdb/v2/reference/glossary/#field-key) and the [data type](/influxdb/v2/reference/glossary/#data-type) of their [field values](/influxdb/v2/reference/glossary/#field-value).

### Syntax

```sql
SHOW FIELD KEYS [ON <database_name>] [FROM <measurement_name>]
```

-   `ON <database_name>` is optional. If the query does not include `ON <database_name>`, you must specify the database with `USE <database_name>` when using the [InfluxQL shell](/influxdb/v2/tools/influxql-shell/) or with the `db` query string parameter in the [InfluxDB 1.x compatibility API](/influxdb/v2/reference/api/influxdb-1x/) request.
-   The `FROM` clause is optional. See the Data Exploration page for documentation on the [`FROM` clause](/influxdb/v2/query-data/influxql/explore-data/select/#from-clause).

**Note:** A field’s data type [can differ](/influxdb/v2/reference/faq/#how-does-influxdb-handle-field-type-discrepancies-across-shards) across [shards](/influxdb/v2/reference/glossary/#shard). If your field has more than one type, `SHOW FIELD KEYS` returns the type that occurs first in the following list: float, integer, string, boolean.

### Examples

#### Run SHOW FIELD KEYS with the ON clause

```sql
SHOW FIELD KEYS ON noaa
```

**Output:**

The query returns the field keys and field value data types for each measurement in the `noaa` database.

| name | fieldKey | fieldType |
| --- | --- | --- |
| average_temperature | degrees | float |
| h2o_feet | level description | string |
| h2o_feet | water_level | float |
| h2o_pH | pH | float |
| h2o_quality | index | float |
| hh2o_temperature | degrees | float |

#### Run SHOW FIELD KEYS with the FROM clause

```sql
SHOW FIELD KEYS ON noaa FROM h2o_feet
```

**Output:**

The query returns the fields keys and field value data types for the `h2o_feet` measurement in the `noaa` database.

| name | fieldKey | fieldType |
| --- | --- | --- |
| h2o_feet | level description | string |
| h2o_feet | water_level | float |

### Common Issues with SHOW FIELD KEYS

#### SHOW FIELD KEYS and field type discrepancies

Field value [data types](/influxdb/v2/reference/glossary/#data-type) cannot differ within a [shard](/influxdb/v2/reference/glossary/#shard) but they can differ across shards. `SHOW FIELD KEYS` returns every data type, across every shard, associated with the field key.

##### Example

The `all_the_types` field stores four different data types:

```sql
SHOW FIELD KEYS
```

name: mymeas

| fieldKey | fieldType |
| --- | --- |
| all_the_types | integer |
| all_the_types | float |
| all_the_types | string |
| all_the_types | boolean |

Note that `SHOW FIELD KEYS` handles field type discrepancies differently from `SELECT` statements. For more information, see the [How does InfluxDB handle field type discrepancies across shards?](/enterprise_influxdb/v1/troubleshooting/frequently-asked-questions/#how-does-influxdb-handle-field-type-discrepancies-across-shards).

## SHOW FIELD KEY CARDINALITY

Cardinality is the product of all unique databases, retention policies, measurements, field keys and tag values in your Influx instance. Managing cardinality is important, as high cardinality leads to greater resource usage.

```sql
-- show estimated cardinality of the field key set of current database
SHOW FIELD KEY CARDINALITY
-- show exact cardinality on field key set of specified database
SHOW FIELD KEY EXACT CARDINALITY ON noaa
```

## SHOW TAG KEY CARDINALITY

```sql
-- show estimated tag key cardinality
SHOW TAG KEY CARDINALITY
-- show exact tag key cardinality
SHOW TAG KEY EXACT CARDINALITY
```