select 语句中的多个条件基于值

Question

我有多个ctes。在我的 select 语句中，我必须根据条件过滤值。这是我的查询。

SELECT roadName
    ,sum(roadLength) AS sumRoadLength
    ,avg(elevationDifference) AS eglAvgDepth
    ,avg(elevationDifference) AS pglAvgDepth
    ,
FROM cte3
GROUP BY roadName
ORDER BY roadName

在 "elevationDifference" 下有很多值，范围从 -10 到 +20，分布在 "roadName" 中。我想要完成的是，如果所有 "elevationDifference" 值都 <0 并取平均值，"eglAvgDepth" 将 return。与 pglAvgDepth 相同的情况，其中值 >0.

我尝试添加 where 语句，但仅适用于 eglAvgDepth

WHERE elevationDifference < 0
GROUP BY roadName
ORDER BY roadName

Answer 1

只需添加一个条件表达式：

avg(case when elevationDifference < 0 then elevationDifference end) as eglAvgDepth,
avg(case when elevationDifference > 0 then elevationDifference end) as pglAvgDepth,

编辑：

你已经表达了你想要基于所有值是正数还是负数的值。如果是：

(case when max(elevationDifference) < 0 then avg(elevationDifference) end) as eglAvgDepth,
(case when max(elevationDifference) > 0 then avg(elevationDifference) end) as pglAvgDepth,

select 语句中的多个条件基于值

Multiple conditions in select statement based on values

sql

sql-server

mysql-select-db