错误代码： 1055
Expression #1 of ORDER BY clause is not in GROUP BY clause and contains nonaggregated column ‘xxxx’ which is not functionally dependent on columns in GROUP BY clause; this is incompatible with sql_mode=only_full_group_by
原因
在MySQL5.7.5后，默认开启了ONLY_FULL_GROUP_BY，所以导致了之前的一些SQL无法正常执行，其实，是我们的SQL不规范造成的，因为group by 之后，返回的一些数据是不确定的，所以才会出现这个错误。
解决方案
一、禁用ONLY_FULL_GROUP_BY
Linux环境
1.登录进入MySQL，linux登录的：mysql -u username -p ，然后输入密码，输入SQL：show variables like ‘%sql_mode’;
2. 编辑my.cnf文件，文件地址一般在：/etc/my.cnf，/etc/mysql/my.cnf，找到sql-mode的位置，去掉ONLY_FULL_GROUP_BY，然后重启MySQL；有的my.cnf中没有sql-mode，需要加入：sql-mode=STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION，注意要加入到[mysqld]下面，加入到其他地方，重启后也不生效，具体的如下图：
3.修改成功后重启MySQL服务，service mysql restart，重启好后，再登录mysql，输入SQL：show variables like ‘%sql_mode’; 如果没有ONLY_FULL_GROUP_BY，就说明已经成功了。
Windows下解压版Mysql
去掉ONLY_FULL_GROUP_BY这个配置，需要更改my.ini配置文件中的配置，如果没有则自己创建（一般安装好后按照教程就会创建好这个文件，该配置文件放到mysql安装目录根目录下），配置内容如下：
[mysqld]
#去掉"ONLY_FULL_GROUP_BY"的配置 这个一定写在[mysqld]下面
sql_mode=STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION
#以下两句具体路径改为自己机器上的路径，分别为mysql安装目录以及mysql存放数据的目录
basedir=D:\安装目录\mysql-5.7.21
datadir=D:\安装目录\mysql-5.7.21\data
port=3306
character-set-server=utf8
[client]
port=3306
character-set=utf8
二、 修改SQL，因为出现这个问题，基本都是因为这个问题造成的，不确定返回字段可以使用ANY_VALUE(column_name)。
根据mysql文档，“如果name不是t的主键或唯一的NOT NULL列，则此查询无效。在这种情况下，不可以推断出功能依赖性并发生错误：“
SELECT name, address, MAX(age) FROM t GROUP BY name;
ERROR 1055 (42000): Expression #2 of SELECT list is not in GROUP
BY clause and contains nonaggregated column 'mydb.t.address' which
is not functionally dependent on columns in GROUP BY clause; this
is incompatible with sql_mode=only_full_group_by
修改ANY_VALUE(‘my_column_name’) my_column_name “在这种情况下，MySQL忽略每个名称组中的地址值的不确定性并接受查询。” 使用ANY_VALUE（）来引用地址：
修改后语句如下
SELECT name, ANY_VALUE(address), MAX(age) FROM t GROUP BY name;
最后附自己修改项目中的一条语句供大家参考
#表结构如下所示
DROP TABLE IF EXISTS `message`;
CREATE TABLE `message` (
`id` INT NOT NULL AUTO_INCREMENT,
`from_id` INT NULL,
`to_id` INT NULL,
`content` TEXT NULL,
`created_date` DATETIME NULL,
`has_read` INT NULL,
`conversation_id` VARCHAR(45) NOT NULL,
PRIMARY KEY (`id`),
INDEX `conversation_index` (`conversation_id` ASC),
INDEX `created_date` (`created_date` ASC))
ENGINE = InnoDB
DEFAULT CHARACTER SET = utf8;
#Mysql5.7.5之前语句
SELECT from_id , to_id, content, has_read, conversation_id, created_date,COUNT(id) FROM (
SELECT id,from_id,to_id,content,created_date,has_read,conversation_id FROM message
WHERE from_id=12 OR to_id=12 ORDER BY created_date DESC)
AS tt GROUP BY conversation_id
ORDER BY created_date
DESC LIMIT 0, 10;
#修改后
SELECT any_value (from_id) , any_value (to_id), any_value (content), any_value (has_read), any_value (conversation_id), any_value(created_date),any_value(COUNT(id)) AS id FROM (
SELECT id,from_id,to_id,content,created_date,has_read,conversation_id FROM message
WHERE from_id=12 OR to_id=12 ORDER BY created_date DESC)
AS tt GROUP BY conversation_id
ORDER BY any_value(created_date)
DESC LIMIT 0, 10;
# 如果是以前的老项目重构，保持列名一致就不需要修改原程序，通过起别名适配 如下所示
SELECT any_value (from_id) AS from_id, any_value (to_id) AS to_id, any_value (content) AS content, any_value (has_read) AS has_read,
any_value (conversation_id) AS conversation_id, any_value(created_date) AS created_date,any_value(COUNT(id)) AS id FROM (
SELECT id,from_id,to_id,content,created_date,has_read,conversation_id FROM message
WHERE from_id=12 OR to_id=12 ORDER BY created_date DESC)
AS tt GROUP BY conversation_id
ORDER BY any_value(created_date)
DESC LIMIT 0, 10;
参考博客：
https://www.cnblogs.com/tygtyg/p/9895481.html
https://www.jianshu.com/p/a430fa1deb85
https://cloud.tencent.com/developer/ask/198993/answer/310023