lead

Documentação da função de janela lead

Retorna um valor avaliado na linha que está offset linhas após a linha atual dentro do frame ordenado. Esta função é semelhante a leadInFrame, mas sempre usa o frame ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING.

Sintaxe

lead(x[, offset[, default]])
  OVER ([[PARTITION BY grouping_column] [ORDER BY sorting_column]] | [window_name])
FROM table_name
WINDOW window_name as ([[PARTITION BY grouping_column] [ORDER BY sorting_column])

Para mais detalhes sobre a sintaxe de funções de janela, consulte: Funções de janela - Sintaxe.

Parâmetros

• x — Nome da coluna.
• offset — Deslocamento a ser aplicado. (U)Int*. (Opcional — 1 por padrão).
• default — Valor a ser retornado se a linha calculada exceder os limites do frame da janela. (Opcional — valor padrão do tipo da coluna quando omitido).

Valor retornado

• valor avaliado na linha situada offset linhas após a linha atual dentro do frame ordenado.

Exemplo

Este exemplo analisa dados históricos de vencedores do Prêmio Nobel e usa a função lead para retornar uma lista de vencedores consecutivos na categoria de física.

Query

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

Query

SELECT
    fullName,
    lead(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

Query

   ┌─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                        │
   └──────────────────┴──────┴──────────┴────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘