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InfluxDB Cloud Serverless

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.

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

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

Examples

Union results from different measurements

(  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

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.

(  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

Union query results with custom data

The following example uses the sample data set provided in Get started with InfluxDB tutorial. It also uses the table value constructor to build a table with custom data.

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

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