Question

我发布了in this link 但我应该发布一个新的

我是MySQL的初学者我尝试过上面的链接，但得到一些错误代码

MY select看起来像这样

SELECT YEAR(TimeStamp) AS "YEAR", MONTHNAME(TimeStamp) AS "MONTH", DAY(TimeStamp) AS "DAY",
       min(Temperature) AS "min", max(Temperature) AS "max",
       ROUND(AVG(Temperature),1) AS "avg",
       substring_index(group_concat(TimeStamp order by Temperature asc), ',', 1) as min_TimeStamp,
       substring_index(group_concat(TimeStamp order by Temperature desc), ',', 1) as max_TimeStamp
FROM ute_temp_min
    WHERE TimeStamp BETWEEN '2014-11-05' and NOW()
GROUP BY YEAR(TimeStamp), MONTH(TimeStamp),  DAY(TimeStamp);

这是我的输入表

index","TimeStamp","Temperature"
2721909,"2014-11-05 00:00:08",1.4
2721910,"2014-11-05 00:01:12",1.4
2721911,"2014-11-05 00:02:13",1.4
2721912,"2014-11-05 00:03:06",1.4

这是我的输出，它看起来没问题

"YEAR","MONTH","DAY","min","max","avg","min_TimeStamp","max_TimeStamp"
2014,"November",5,-3.4,1.4,-0.6,"2014-11-05 22:15:16","2014-11-05 00:28:12"
2014,"November",6,-2.6,0.3,-0.9,"2014-11-06 01:34:08","2014-11-06 12:52:12"

但我得到了这个错误（更多但是相同但不同的行

Row 52 was cut by GROUP_CONCAT() errornr 1260

我的错误是什么？

SvenÅke

Answer 1

尝试设置会话最大长度。我整个星期都在使用它来修复我们服务器上的数据完整性问题，所以group concat对此非常有用（直观地看到那些不应该链接在一起的用户）但是我也遇到了数据被切断的问题

试试这个

SET SESSION group_concat_max_len = 999999999;
SELECT ... -- your query here

关于这个的很棒的事情是它只在你的当前会话（它是一个临时函数）..所以你不是在服务器上分配内存（磁盘空间）所以它不会慢事情发生了。会话结束后，长度会更改回默认值（1024）！

编辑：

对您的查询进行一点清理

SELECT 
    YEAR(TimeStamp) AS "YEAR", 
    MONTHNAME(TimeStamp) AS "MONTH", 
    DAY(TimeStamp) AS "DAY",
    min(Temperature) AS "min", 
    max(Temperature) AS "max",
    ROUND(AVG(Temperature),1) AS "avg",
    substring_index(group_concat(TimeStamp order by Temperature asc), ',', 1) as min_TimeStamp,
    substring_index(group_concat(TimeStamp order by Temperature desc), ',', 1) as max_TimeStamp
FROM ute_temp_min
WHERE DATE(TimeStamp) BETWEEN '2014-11-05' and CURDATE()
GROUP BY DATE(TimeStamp);

注意我更改了WHERE进行日期比较（因此MySQL不必将您的字符串日期自行转换为日期时间）
我还将GROUP BY更改为DATE（）以进行更少的计算

group_concat上的Mysql错误

1 个答案:

编辑：