ClickHouse/docs/en/sql-reference/window-functions/first_value.md

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first_value

Returns the first value evaluated within its ordered frame. By default, NULL arguments are skipped, however the RESPECT NULLS modifier can be used to override this behaviour.

Syntax

first_value (column_name) [[RESPECT NULLS] | [IGNORE NULLS]]
  OVER ([[PARTITION BY grouping_column] [ORDER BY sorting_column] 
        [ROWS or RANGE expression_to_bound_rows_withing_the_group]] | [window_name])
FROM table_name
WINDOW window_name as ([[PARTITION BY grouping_column] [ORDER BY sorting_column])

Alias: any.

:::note Using the optional modifier RESPECT NULLS after first_value(column_name) will ensure that NULL arguments are not skipped. See NULL processing for more information. :::

For more detail on window function syntax see: Window Functions - Syntax.

Returned value

• The first value evaluated within its ordered frame.

Example

In this example the first_value function is used to find the highest paid footballer from a fictional dataset of salaries of Premier League football players.

Query:

DROP TABLE IF EXISTS salaries;
CREATE TABLE salaries
(
    `team` String,
    `player` String,
    `salary` UInt32,
    `position` String
)
Engine = Memory;

INSERT INTO salaries FORMAT Values
    ('Port Elizabeth Barbarians', 'Gary Chen', 196000, 'F'),
    ('New Coreystad Archdukes', 'Charles Juarez', 190000, 'F'),
    ('Port Elizabeth Barbarians', 'Michael Stanley', 100000, 'D'),
    ('New Coreystad Archdukes', 'Scott Harrison', 180000, 'D'),
    ('Port Elizabeth Barbarians', 'Robert George', 195000, 'M'),
    ('South Hampton Seagulls', 'Douglas Benson', 150000, 'M'),
    ('South Hampton Seagulls', 'James Henderson', 140000, 'M');

SELECT player, salary, 
       first_value(player) OVER (ORDER BY salary DESC) AS highest_paid_player
FROM salaries;

Result:

   ┌─player──────────┬─salary─┬─highest_paid_player─â”<C3A2>
1. │ Gary Chen       │ 196000 │ Gary Chen           │
2. │ Robert George   │ 195000 │ Gary Chen           │
3. │ Charles Juarez  │ 190000 │ Gary Chen           │
4. │ Scott Harrison  │ 180000 │ Gary Chen           │
5. │ Douglas Benson  │ 150000 │ Gary Chen           │
6. │ James Henderson │ 140000 │ Gary Chen           │
7. │ Michael Stanley │ 100000 │ Gary Chen           │
   └─────────────────┴────────┴─────────────────────┘