如何通过RANK语句使用条件

编程问答 2022-06-03

问题描述

下面的代码完成了它的工作：它为我提供了每个类别的前10个结果。

SELECT *
FROM (
SELECT *,RANK() OVER (PARTITION BY "pera_id" ORDER BY "surface" DESC) AS rnk
FROM "testBadaBing"
) AS x
WHERE rnk <= 10

现在，我想添加条件，以便结果的数量可以根据条件而有所不同。例子：如果“ note” = 1，那么我想保留1个结果，否则取3。

我尝试过使用CASE WHEN语句在下面看到的内容，但是您可能希望它不起作用。返回错误：

1-在“ CASE”附近：语法错误

SELECT *
CASE WHEN "note" = 1 THEN
SELECT *
    FROM (
        SELECT *,RANK() OVER (PARTITION BY "pera_id" ORDER BY "surface" DESC) AS rnk
        FROM "testBadaBing"
    ) AS x
WHERE rnk <= 1
ELSE
SELECT *
    FROM (
        SELECT *,RANK() OVER (PARTITION BY "pera_id" ORDER BY "surface" DESC) AS rnk
        FROM "testBadaBing"
    ) AS x
WHERE rnk <= 3
END

您对如何进行这项工作有任何想法吗？我对sql的了解非常有限。当我在QGIS环境中工作时，代码必须与sqlite / SpatiaLite兼容。谢谢。

解决方法

您可以在外部查询的WHERE子句中使用布尔逻辑：

SELECT *
FROM (
    SELECT t.*,RANK() OVER (PARTITION BY "pera_id" ORDER BY "surface" DESC) AS rnk
    FROM "testBadaBing" t
) AS x
WHERE ("note" = 1 and rnk = 1) OR rnk <= 3
conditional-statementsrankingspatialitesqlsqlsqlite