php Mysql减去前一个索引

Question

我正在制作一个项目，它接收来自用水户的数据，然后我使用 chart.js 在图表中显示这些值。问题是我必须在查询中进行一些计算。

我已经完成了第一个，即读数指数除以每单位脉冲数 (/1000)

但我还是要做另一个就是下一个索引减去旧索引，基本上是 OldIndex = (IndexReleve/ImpParUnit) 所以 (NewIndex - OldIndex )

但是同一个查询中的所有内容我都有问题，我不知道是否有解决方案......

提前感谢您的帮助

输入数据示例 oldindex = 343.32 NewIndex = (IndexReleve/ImpParUnit) - oldindex = 471.56 - 343.32 = 128.24

OldIndex = 128.24 NewIndex = (IndexReleve/ImpParUnit) - oldindex = 921.56 - 128.24 = 793.32 等等……

Releves = 从用水户处收到的值 就位=每个用水者的地方，因为有不同的公园

SELECT 
   ROUND((IndexReleve/ImpParUnit),2) As IndexReel,
   CONCAT(DATE_FORMAT(DateHeure, '%d/%m/%Y'), 
   '\n', 
   DATE_FORMAT(DateHeure,' %H:%i:%s') ) as DateHeure 
FROM Releves,Emplacements

Answer 1

你的情况可以试试

select 
   t.IndexReel,t.IndexReel-LAG(t.IndexReel,1) over() as whatuwant,
   ROUND((IndexReleve/ImpParUnit),2) As IndexReel,
   CONCAT(DATE_FORMAT(DateHeure, '%d/%m/%Y'), 
   '\n', 
   DATE_FORMAT(DateHeure,' %H:%i:%s') ) as DateHeure 
FROM Releves,Emplacements) t 

没有LAG试试这个：

select DateHeure,ANY_VALUE(IndexReel),ANY_VALUE(whatuwant) from ( 
    select ANY_VALUE(DateHeure) as DateHeure,ANY_VALUE(IndexReel) as IndexReel,sum(IndexReel) as whatuwant from (
        select @index:=@index +1 as idx,t.IndexReel,'\n',t.DateHeure from (SELECT 
   ROUND((IndexReleve/ImpParUnit),2) As IndexReel,
   CONCAT(DATE_FORMAT(DateHeure, '%d/%m/%Y'), 
   '\n', 
   DATE_FORMAT(DateHeure,' %H:%i:%s') ) as DateHeure 
FROM Releves,Emplacements) t,(select @index:=0) r UNION ALL     
        select @index2:=@index2 +1 as idx,0-t.IndexReel as IndexReel,'\n',t.DateHeure from (SELECT 
   ROUND((IndexReleve/ImpParUnit),2) As IndexReel,
   CONCAT(DATE_FORMAT(DateHeure, '%d/%m/%Y'), 
   '\n', 
   DATE_FORMAT(DateHeure,' %H:%i:%s') ) as DateHeure 
FROM Releves,Emplacements) t,(select @index2:=1) r
    ) t group by idx 
) t group by DateHeure