FIRST_VALUE

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

Last modified: February 16, 2023

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