Important

The SingleStore 9.1 release candidate (RC) is available now. It will be promoted to general availability (GA) soon and at that time it will be renamed to SingleStore 10.

In the interim, SingleStore 9.1 RC can be used to preview, evaluate, and provide feedback on the new and upcoming features in SingleStore 10, while SingleStore 9.0 is recommended for production workloads.

FIRST_VALUE

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

SQL

CREATE TABLE fv_example (a INT, b INT);

INSERT INTO fv_example VALUES (1, 2), (2, 2), (3, 3), (4, 3);

SQL

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

SQL

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 |
+------+-----------------------------------+

SQL

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

SQL

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 |
+------+---------------------------------------------------+