Combine Results With UNION ALL

Append result sets together without removing duplicates.

5/5 supported engines validation-green 1 example 2 scenarios

Docker-validated Not currently validation-green

Example 1

Combine two result sets and keep duplicates

Unlike UNION, UNION ALL keeps both Linus rows in the final output.

Source table data Rows loaded before the example query runs.

Setup

CREATE TABLE morning (name VARCHAR(50));

CREATE TABLE evening (name VARCHAR(50));

INSERT INTO
  morning (name)
VALUES
  ('Ada'),
  ('Linus');

INSERT INTO
  evening (name)
VALUES
  ('Linus'),
  ('Grace');

Validated query Shared across supported engines.

SQL

SELECT
  name
FROM
  morning
UNION ALL
SELECT
  name
FROM
  evening
ORDER BY
  name;

Expected result Returned rows for the shared example.

name
Ada
Grace
Linus
Linus

The preserved duplicate row is the key behavior shown here.

Useful when

Where this command helps.

combining event streams where duplicates are meaningful
merging multiple query branches without paying deduplication cost

Explanation

What the command is doing.

UNION ALL stacks the rows from multiple queries and preserves duplicates. It is usually faster than UNION because the database does not need to deduplicate the combined output.

Combine Results With UNION ALL

Combine two result sets and keep duplicates

Where this command helps.

What the command is doing.

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