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

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leadInFrame

Returns a value evaluated at the row that is offset rows after the current row within the ordered frame.

:::warning leadInFrame behavior differs from the standard SQL lead window function. Clickhouse window function leadInFrame respects the window frame. To get behavior identical to the lead, use ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING. :::

Syntax

leadInFrame(x[, offset[, default]])
  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])

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

Parameters

• x — Column name.
• offset — Offset to apply. (U)Int*. (Optional - 1 by default).
• default — Value to return if calculated row exceeds the boundaries of the window frame. (Optional - default value of column type when omitted).

Returned value

• value evaluated at the row that is offset rows after the current row within the ordered frame.

Example

This example looks at historical data for Nobel Prize winners and uses the leadInFrame function to return a list of successive winners in the physics category.

Query:

CREATE OR REPLACE VIEW nobel_prize_laureates
AS SELECT *
FROM file('nobel_laureates_data.csv');

SELECT
    fullName,
    leadInFrame(year, 1, year) OVER (PARTITION BY category ORDER BY year ASC
      ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING
    ) AS year,
    category,
    motivation
FROM nobel_prize_laureates
WHERE category = 'physics'
ORDER BY year DESC
LIMIT 9

Result:

   ┌─fullName─────────┬─year─┬─category─┬─motivation─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┐
1. │ Anne L Huillier  │ 2023 │ physics  │ for experimental methods that generate attosecond pulses of light for the study of electron dynamics in matter                     │
2. │ Pierre Agostini  │ 2023 │ physics  │ for experimental methods that generate attosecond pulses of light for the study of electron dynamics in matter                     │
3. │ Ferenc Krausz    │ 2023 │ physics  │ for experimental methods that generate attosecond pulses of light for the study of electron dynamics in matter                     │
4. │ Alain Aspect     │ 2022 │ physics  │ for experiments with entangled photons establishing the violation of Bell inequalities and  pioneering quantum information science │
5. │ Anton Zeilinger  │ 2022 │ physics  │ for experiments with entangled photons establishing the violation of Bell inequalities and  pioneering quantum information science │
6. │ John Clauser     │ 2022 │ physics  │ for experiments with entangled photons establishing the violation of Bell inequalities and  pioneering quantum information science │
7. │ Giorgio Parisi   │ 2021 │ physics  │ for the discovery of the interplay of disorder and fluctuations in physical systems from atomic to planetary scales                │
8. │ Klaus Hasselmann │ 2021 │ physics  │ for the physical modelling of Earths climate quantifying variability and reliably predicting global warming                        │
9. │ Syukuro Manabe   │ 2021 │ physics  │ for the physical modelling of Earths climate quantifying variability and reliably predicting global warming                        │
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