MySql 5.7 ORDER BY 子句不在 GROUP BY 子句中且包含非聚合列

Question

我想在 my.ini

中禁用 "only_full_group_by" 的情况下找出答案

这是我的查询：

SELECT 
  p.title,
  COUNT(t.qty) AS total 
FROM
  payments t 
  LEFT JOIN products AS p 
    ON p.id = t.item 
WHERE t.user = 1 
GROUP BY t.item
ORDER BY t.created DESC;

和表格：

付款：

id     item   user   created
============================
1      1      1      2017-01-10
2      2      1      2017-01-11
3      3      1      2017-01-12
4      4      1      2017-01-13
5      1      1      2017-01-14

产品：

id     title    created
==========================
1      First     2016-12-10
1      Second    2016-12-11
1      Third     2016-12-12
1      Fourth    2016-12-13

最后的结果应该看谎言：

Name    Total
First   2
Second  1
Third   1
Fourth  1

但是，如果我将查询更改为 GROUP BY t.item, t.created，错误就消失了，但我最终得到了 5 条记录，而不是 4 条，这不是我想要的。由于我根据 "item" 字段对项目进行分组，因此应该只有四个记录

Answer 1

对我来说，你应该按 p.title

分组查询

  SELECT 
    p.title,
    COUNT(t.qty) AS total 
  FROM
    payments t 
    LEFT JOIN products AS p 
      ON p.id = t.item 
  WHERE t.user = 1 
  GROUP BY p.title;

或

  SELECT 
    p.title,
    COUNT(t.qty) AS total 
  FROM
    payments t 
    LEFT JOIN products AS p 
      ON p.id = t.item 
  WHERE t.user = 1 
  GROUP BY p.title
  order by p.created;

然后对于 "But if I change my query to GROUP BY t.item, t.created Error is gone" 请记住，从 mysql 5.7 开始，如果您使用 selected 列而不在 group by 中，您会出错..

如果你真的需要，你可以禁用 sql 模式的适当设置，例如

SET sql_mode = ''

https://dev.mysql.com/doc/refman/5.7/en/sql-mode.html

最后一列按顺序对分组依据和 ONLY_FULL_GROUP_BY 参数没有影响 .. 但是如果我按顺序排列的列不在 select 中实际上没有意义

Answer 2

第 1 项有两个 t.created。因此请决定要按哪个排序。例如：

ORDER BY MIN(t.created) DESC;

Answer 3

这是您的查询：

SELECT p.title, COUNT(t.qty) AS total 
-------^
FROM payments t LEFT JOIN
     products AS p 
     ON p.id = t.item 
WHERE t.user = 1 
GROUP BY t.item
---------^
ORDER BY t.created DESC;
---------^

指向的地方有问题。请注意 SELECT 和 GROUP BY 指的是不同的列。在 LEFT JOIN 中，您（几乎）总是希望通过 第一个 table 中的内容进行聚合，而不是第二个

ORDER BY 是另一个问题。您没有按此列进行聚合，因此您需要确定所需的值。我猜 MIN() 或 MAX():

SELECT p.title, COUNT(t.qty) AS total 
FROM payments t LEFT JOIN
     products AS p 
     ON p.id = t.item 
WHERE t.user = 1 
GROUP BY p.title
ORDER BY MAX(t.created) DESC;

我还要补充说 COUNT(t.qty) 是可疑的。通常 qty 指的是 "quantity" 而你想要的是总和：SUM(t.qty).

MySql 5.7 ORDER BY 子句不在 GROUP BY 子句中且包含非聚合列

MySql 5.7 ORDER BY clause is not in GROUP BY clause and contains nonaggregated column

mysql

sql

group-by

mysql-error-1055