---
title: UNION clause
description: The UNION clause combines the results of two or more SELECT statements into a single result set.
url: https://docs.influxdata.com/influxdb3/clustered/reference/sql/union/
estimated_tokens: 5283
product: InfluxDB Clustered
version: clustered
---

# UNION clause

The `UNION` clause combines the results of two or more `SELECT` statements into a single result set. By default, `UNION` only keeps unique rows. To keep all rows, including duplicates, use `UNION ALL`.

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

**When using the `UNION` clause**:

-   The number of columns in each result set must be the same.
-   Columns must be in the same order and of the same or compatible data types.

## Syntax

```sql
SELECT expression[,...n]
FROM measurement_1
UNION [ALL]
SELECT expression[,...n]
FROM measurement_2
```

## Examples

-   [Union results from different measurements](#union-results-from-different-measurements)
-   [Return the highest and lowest three results in a single result set](#return-the-highest-and-lowest-three-results-in-a-single-result-set)
-   [Union query results with custom data](#union-query-results-with-custom-data)

### Union results from different measurements

```sql
(
  SELECT
    'h2o_pH' AS measurement,
    time,
    "pH" AS "water_pH"
  FROM "h2o_pH"
  LIMIT 4
)
UNION
(
  SELECT
    'h2o_quality' AS measurement,
    time,
    index
  FROM h2o_quality
  LIMIT 4
)
```

[](#view-example-results)

View example results

| measurement | time | water_pH |
| --- | --- | --- |
| h2o_pH | 2019-08-27T00:12:00Z | 7 |
| h2o_pH | 2019-08-27T00:18:00Z | 8 |
| h2o_quality | 2019-09-11T01:06:00Z | 89 |
| h2o_pH | 2019-08-27T00:06:00Z | 7 |
| h2o_quality | 2019-09-11T00:00:00Z | 26 |
| h2o_quality | 2019-09-11T01:00:00Z | 19 |
| h2o_quality | 2019-09-11T00:48:00Z | 65 |
| h2o_pH | 2019-08-27T00:00:00Z | 8 |

### Return the highest and lowest three results in a single result set

*The following example uses the sample data set provided in [Get started with InfluxDB tutorial](/influxdb3/clustered/get-started/write/#construct-line-protocol).*

```sql
(
  SELECT
    'low' as type,
    time,
    co
  FROM home
  ORDER BY co ASC
  LIMIT 3
)
UNION 
(
  SELECT
    'high' as type,
    time,
    co
  FROM home
  ORDER BY co DESC
  LIMIT 3
)
```

[](#view-example-results)

View example results

| type | time | co |
| --- | --- | --- |
| high | 2022-01-01T20:00:00Z | 26 |
| high | 2022-01-01T19:00:00Z | 22 |
| high | 2022-01-01T18:00:00Z | 18 |
| low | 2022-01-01T14:00:00Z | 0 |
| low | 2022-01-01T10:00:00Z | 0 |
| low | 2022-01-01T08:00:00Z | 0 |

### Union query results with custom data

*The following example uses the sample data set provided in [Get started with InfluxDB tutorial](/influxdb3/clustered/get-started/write/#construct-line-protocol). It also uses the [table value constructor](/influxdb3/clustered/reference/sql/table-value-constructor/) to build a table with custom data.*

```sql
SELECT *
FROM home
WHERE
  time >= '2022-01-01T08:00:00Z'
  AND time <= '2022-01-01T12:00:00Z'
UNION
SELECT * FROM
  (VALUES (0, 34.2, 'Bedroom', 21.1, '2022-01-01T08:00:00Z'::TIMESTAMP),
          (0, 34.5, 'Bedroom', 21.2, '2022-01-01T09:00:00Z'::TIMESTAMP),
          (0, 34.6, 'Bedroom', 21.5, '2022-01-01T10:00:00Z'::TIMESTAMP),
          (0, 34.5, 'Bedroom', 21.8, '2022-01-01T11:00:00Z'::TIMESTAMP),
          (0, 33.9, 'Bedroom', 22.0, '2022-01-01T12:00:00Z'::TIMESTAMP)
  ) newRoom(co, hum, room, temp, time)
ORDER BY room, time
```

[](#view-example-results)

View example results

| co | hum | room | temp | time |
| --- | --- | --- | --- | --- |
| 0 | 34.2 | Bedroom | 21.1 | 2022-01-01T08:00:00Z |
| 0 | 34.5 | Bedroom | 21.2 | 2022-01-01T09:00:00Z |
| 0 | 34.6 | Bedroom | 21.5 | 2022-01-01T10:00:00Z |
| 0 | 34.5 | Bedroom | 21.8 | 2022-01-01T11:00:00Z |
| 0 | 33.9 | Bedroom | 22 | 2022-01-01T12:00:00Z |
| 0 | 35.9 | Kitchen | 21 | 2022-01-01T08:00:00Z |
| 0 | 36.2 | Kitchen | 23 | 2022-01-01T09:00:00Z |
| 0 | 36.1 | Kitchen | 22.7 | 2022-01-01T10:00:00Z |
| 0 | 36 | Kitchen | 22.4 | 2022-01-01T11:00:00Z |
| 0 | 36 | Kitchen | 22.5 | 2022-01-01T12:00:00Z |
| 0 | 35.9 | Living Room | 21.1 | 2022-01-01T08:00:00Z |
| 0 | 35.9 | Living Room | 21.4 | 2022-01-01T09:00:00Z |
| 0 | 36 | Living Room | 21.8 | 2022-01-01T10:00:00Z |
| 0 | 36 | Living Room | 22.2 | 2022-01-01T11:00:00Z |
| 0 | 35.9 | Living Room | 22.2 | 2022-01-01T12:00:00Z |