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Important

Helios features are now enabled during weekly update windows and are no longer directly tied to SingleStore engine releases. Refer to the release notes to view the latest features available in your Helios cluster.

FIRST_VALUE

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The FIRST_VALUE() function returns an expression evaluated at the first row of the window frame.

If there are no rows in the frame, returns NULL. For an overview of window functions in SingleStore Helios, see Window Functions Guide.

Syntax

FIRST_VALUE ( expression ) OVER (
    [PARTITION BY (col | expr), ...]
    [ORDER BY (col | expr), ...]
    [frame_clause]
)

Arguments

  • expression: any expression. This may be a column name, the result of another function, or a math operation.

Return Type

The result type of expression

Examples

CREATE TABLE fv_example (a INT, b INT);


INSERT INTO fv_example VALUES (1, 2), (2, 2), (3, 3), (4, 3);
CREATE TABLE tick_table(TIMESTAMP DATETIME(6), symbol VARCHAR(5), comp_name VARCHAR (30), price NUMERIC(18,4));




INSERT INTO tick_table VALUES('2022-11-18 10:55:36.000000','STC','SomeTechCo', 100.00),
('2022-11-18 10:55:37.000000','STC','SomeTechCo', 102.00),
('2022-11-18 10:55:42.000000', 'STC', 'SomeTechCo', 105.00),
('2022-11-18 10:55:48.000000', 'STC', 'SomeTechCo', 101.00),
('2022-11-18 10:56:03.000000', 'STC', 'SomeTechCo', 99.00),
('2022-11-18 10:55:42.000000', 'AME', 'ACME', 198.00),
('2022-11-18 10:55:50.000000', 'AME', 'ACME', 208.00),
('2022-11-18 10:55:52.000000', 'AME', 'ACME', 210.00),
('2022-11-18 10:55:55.000000', 'AME', 'ACME', 211.00),
('2022-11-18 10:55:52.000000', 'OCO', 'OnCallCo', 21.00),
('2022-11-18 10:55:55.000000', 'OCO', 'OnCallCo', 22.00),
('2022-11-18 10:55:57.000000', 'OCO', 'OnCallCo', 21.00),
('2022-11-18 10:56:00.000000', 'OCO', 'OnCallCo', 23.00),
('2022-11-18 10:56:03.000000', 'OCO', 'OnCallCo', 24.00);

Window Function

SELECT a, FIRST_VALUE(a) OVER (ORDER BY a)
FROM fv_example;
+------+-----------------------------------+
| a    | FIRST_VALUE(a) OVER(ORDER BY (a)) |
+------+-----------------------------------+
|    1 |                                 1 |
|    2 |                                 1 |
|    3 |                                 1 |
|    4 |                                 1 |
+------+-----------------------------------+
SELECT TIMESTAMP, symbol, price,
       FIRST_VALUE(price) OVER (PARTITION BY symbol)
FROM tick_table
GROUP BY TIMESTAMP;
+----------------------------+--------+----------+------------------------------------------------+
| TIMESTAMP                  | symbol | price    | FIRST_VALUE(price) OVER (PARTITION BY symbol)  |
+----------------------------+--------+----------+------------------------------------------------+
| 2022-11-18 10:55:50.000000 | AME    | 208.0000 |                                       208.0000 |
| 2022-11-18 10:55:55.000000 | AME    | 211.0000 |                                       208.0000 |
| 2022-11-18 10:55:52.000000 | OCO    |  21.0000 |                                        21.0000 |
| 2022-11-18 10:55:57.000000 | OCO    |  21.0000 |                                        21.0000 |
| 2022-11-18 10:56:00.000000 | OCO    |  23.0000 |                                        21.0000 |
| 2022-11-18 10:56:03.000000 | OCO    |  24.0000 |                                        21.0000 |
| 2022-11-18 10:55:36.000000 | STC    | 100.0000 |                                       100.0000 |
| 2022-11-18 10:55:48.000000 | STC    | 101.0000 |                                       100.0000 |
| 2022-11-18 10:55:42.000000 | STC    | 105.0000 |                                       100.0000 |
| 2022-11-18 10:55:37.000000 | STC    | 102.0000 |                                       100.0000 |
+----------------------------+--------+----------+------------------------------------------------+

Window Frame Clause

SELECT a, FIRST_VALUE(a) OVER (
    ORDER BY a
    ROWS BETWEEN CURRENT ROW AND UNBOUNDED FOLLOWING
)
FROM fv_example;
+------+---------------------------------------------------+
| a    | FIRST_VALUE(a) OVER(ORDER BY (a)                  |
|      | ROWS BETWEEN CURRENT ROW AND UNBOUNDED FOLLOWING) |
+------+---------------------------------------------------+
|    1 |                                                 1 |
|    2 |                                                 2 |
|    3 |                                                 3 |
|    4 |                                                 4 |
+------+---------------------------------------------------+

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Verification instructions

Note: You must install cosign to verify the authenticity of the SingleStore file.

Use the following steps to verify the authenticity of singlestoredb-server, singlestoredb-toolbox, singlestoredb-studio, and singlestore-client SingleStore files that have been downloaded.

You may perform the following steps on any computer that can run cosign, such as the main deployment host of the cluster.

  1. (Optional) Run the following command to view the associated signature files.

    curl undefined

  2. Download the signature file from the SingleStore release server.

    • Option 1: Click the Download Signature button next to the SingleStore file.

    • Option 2: Copy and paste the following URL into the address bar of your browser and save the signature file.

    • Option 3: Run the following command to download the signature file.

      curl -O undefined

  3. After the signature file has been downloaded, run the following command to verify the authenticity of the SingleStore file.

    echo -n undefined |
        cosign verify-blob --certificate-oidc-issuer https://oidc.eks.us-east-1.amazonaws.com/id/CCDCDBA1379A5596AB5B2E46DCA385BC \
          --certificate-identity https://kubernetes.io/namespaces/freya-production/serviceaccounts/job-worker \
          --bundle undefined \
          --new-bundle-format -
    Verified OK

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