相邻列中同一行中的MIN MAX的每日DATETIME

Question

寻找此查询的一种方法，用于显示当天在相邻列的同一行中最高温度发生的实际DATETIME 。

我一直在寻找并尝试一些事情，但我有点迷失了连接，我认为你需要为此使用它。

当前查询和结果..

SELECT 
    YEAR(tstLocal) AS "YEAR", 
    MONTHNAME(tstLocal) AS "MONTH", 
    DAY(tstLocal) AS "DAY", 
    min(tempC) AS "DAILY MIN TEMP", 
    max(tempC) AS "DAILY MAX TEMP", 
    ROUND(AVG(tempC),1) AS "DAILY AVG TEMP" 
FROM 
    house.outside1 
WHERE 
    YEAR(tstLocal) = '2014' AND MONTH(tstLocal) = '7' 
GROUP BY 
    YEAR(tstLocal), 
    MONTH(tstLocal), 
    DAY(tstLocal); 

什么我需要做的是，这些最小/最大温度发生在DATETIME显示呢？

Answer 1

因为你已经使用了group by，该group_concat()/substring_index()伎俩将工作：

SELECT YEAR(tstLocal) AS "YEAR", MONTHNAME(tstLocal) AS "MONTH", DAY(tstLocal) AS "DAY", 
     min(tempC) AS "DAILY MIN TEMP", max(tempC) AS "DAILY MAX TEMP", 
     ROUND(AVG(tempC),1) AS "DAILY AVG TEMP", 
     substring_index(group_concat(tstlocal order by tempC asc), ',', 1) as min_datetime, 
     substring_index(group_concat(tstlocal order by tempC desc), ',', 1) as max_datetime 
FROM house.outside1 
WHERE YEAR(tstLocal) = '2014' AND MONTH(tstLocal) = '7' 
GROUP BY YEAR(tstLocal), MONTH(tstLocal), DAY(tstLocal);