相鄰列中同一行中的MIN MAX的每日DATETIME

Question

尋找此查詢的一種方法，用於顯示當天在相鄰列的同一行中最高溫度發生的實際DATETIME 。

我一直在尋找並嘗試一些事情，但我有點迷失了連接，我認爲你需要爲此使用它。

當前查詢和結果..

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); 

什麼我需要做的是，這些最小/最大溫度發生在DATETIME顯示呢？

Answer 1

因爲你已經使用了group by，該group_concat()/substring_index()伎倆將工作：

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);