GROUP BY上的日期排序顺序，平均值

Question

请参阅以下查询。

SELECT date_format(`date`, '%d %b %Y') AS Datum, 
       AVG(NULLIF(`temp` ,0)) AS Temp, 
       AVG(NULLIF(`cod` ,0)) AS CZV, 
       AVG(NULLIF(`nh4` ,0)) AS NH4 
FROM reactor1 
  GROUP BY `datum` DESC

这将返回正确的数据，但日期的排序顺序不正确。它按日排序日期。

01-NOV
05-NOV
07-DEC
09-DEC
13-NOV

我在这里做错了什么？

Answer 1

试试这个

SELECT date_format(`date`, '%d %b %Y') AS Datum, 
       AVG(NULLIF(`temp` ,0)) AS Temp, 
       AVG(NULLIF(`cod` ,0)) AS CZV, 
       AVG(NULLIF(`nh4` ,0)) AS NH4 
FROM reactor1 
  GROUP BY `Datum` ORDER BY `Datum` DESC

Answer 2

试试这个：

SELECT DATE_FORMAT(r.date, '%d %b %Y') AS Datum, 
       AVG(NULLIF(r.temp, 0)) AS Temp, 
       AVG(NULLIF(r.cod, 0)) AS CZV, 
       AVG(IFNULL(r.nh4, 0)) AS NH4 
FROM reactor1 r 
GROUP BY DATE(r.date) 
ORDER BY DATE(r.date) DESC;