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79 lines
4.5 KiB
Markdown
79 lines
4.5 KiB
Markdown
---
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slug: /en/sql-reference/window-functions/leadInFrame
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sidebar_label: leadInFrame
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sidebar_position: 10
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---
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# leadInFrame
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Returns a value evaluated at the row that is offset rows after the current row within the ordered frame.
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:::warning
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`leadInFrame` behavior differs from the standard SQL `lead` window function.
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Clickhouse window function `leadInFrame` respects the window frame.
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To get behavior identical to the `lead`, use `ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING`.
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:::
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**Syntax**
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```sql
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leadInFrame(x[, offset[, default]])
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OVER ([[PARTITION BY grouping_column] [ORDER BY sorting_column]
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[ROWS or RANGE expression_to_bound_rows_withing_the_group]] | [window_name])
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FROM table_name
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WINDOW window_name as ([[PARTITION BY grouping_column] [ORDER BY sorting_column])
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```
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For more detail on window function syntax see: [Window Functions - Syntax](./index.md/#syntax).
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**Parameters**
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- `x` — Column name.
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- `offset` — Offset to apply. [(U)Int*](../data-types/int-uint.md). (Optional - `1` by default).
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- `default` — Value to return if calculated row exceeds the boundaries of the window frame. (Optional - default value of column type when omitted).
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**Returned value**
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- value evaluated at the row that is offset rows after the current row within the ordered frame.
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**Example**
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This example looks at [historical data](https://www.kaggle.com/datasets/sazidthe1/nobel-prize-data) for Nobel Prize winners and uses the `leadInFrame` function to return a list of successive winners in the physics category.
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Query:
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```sql
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CREATE OR REPLACE VIEW nobel_prize_laureates
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AS SELECT *
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FROM file('nobel_laureates_data.csv');
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```
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```sql
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SELECT
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fullName,
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leadInFrame(year, 1, year) OVER (PARTITION BY category ORDER BY year ASC
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ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING
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) AS year,
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category,
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motivation
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FROM nobel_prize_laureates
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WHERE category = 'physics'
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ORDER BY year DESC
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LIMIT 9
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```
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Result:
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```response
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┌─fullName─────────┬─year─┬─category─┬─motivation─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┐
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1. │ Anne L Huillier │ 2023 │ physics │ for experimental methods that generate attosecond pulses of light for the study of electron dynamics in matter │
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2. │ Pierre Agostini │ 2023 │ physics │ for experimental methods that generate attosecond pulses of light for the study of electron dynamics in matter │
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3. │ Ferenc Krausz │ 2023 │ physics │ for experimental methods that generate attosecond pulses of light for the study of electron dynamics in matter │
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4. │ Alain Aspect │ 2022 │ physics │ for experiments with entangled photons establishing the violation of Bell inequalities and pioneering quantum information science │
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5. │ Anton Zeilinger │ 2022 │ physics │ for experiments with entangled photons establishing the violation of Bell inequalities and pioneering quantum information science │
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6. │ John Clauser │ 2022 │ physics │ for experiments with entangled photons establishing the violation of Bell inequalities and pioneering quantum information science │
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7. │ Giorgio Parisi │ 2021 │ physics │ for the discovery of the interplay of disorder and fluctuations in physical systems from atomic to planetary scales │
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8. │ Klaus Hasselmann │ 2021 │ physics │ for the physical modelling of Earths climate quantifying variability and reliably predicting global warming │
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9. │ Syukuro Manabe │ 2021 │ physics │ for the physical modelling of Earths climate quantifying variability and reliably predicting global warming │
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└──────────────────┴──────┴──────────┴────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘
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```
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