搭建博客时，被mysql的sql_mode中ONLY_FULL_GROUP_BY坑倒了
1、背景
前两天在阿里云服务器上搭建了自己的博客，一切都很顺利，今天在点击归档按钮时，发现是报404。于是我把solo代码在本地运行起来，用本地的mysql数据库，看是否有同样的问题，结果是可以正常访问的。那就看看服务器上的solo日志呗，结果发现了以下报错：
Caused by: org.b3log.latke.repository.RepositoryException: java.sql.SQLSyntaxErrorException: Expression #20 of SELECT list is not in GROUP BY clause and contains nonaggregated column 'solo.aa.oId' which is not functionally dependent on columns in GROUP BY clause; this is incompatible with sql_mode=only_full_group_by原来，这个问题出现在MySQL5.7后版本上，默认的sql_mode值是这样的：
ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION那么sql_mode 有哪些配置？都代表什么意思？
2、sql_mode 配置解析
ONLY_FULL_GROUP_BY
对于GROUP BY聚合操作，如果在SELECT中的列，没有在GROUP BY中出现，那么这个SQL是不合法的，因为列不在GROUP BY从句中。简而言之，就是SELECT后面接的列必须被GROUP BY后面接的列所包含。如：
select a,b from table group by a,b,c; (正确)
select a,b,c from table group by a,b; (错误)这个配置会使得GROUP BY语句环境变得十分狭窄，所以一般都不加这个配置
NO_AUTO_VALUE_ON_ZERO
该值影响自增长列的插入。默认设置下，插入0或NULL代表生成下一个自增长值。（不信的可以试试，默认的sql_mode你在自增主键列设置为0，该字段会自动变为最新的自增值，效果和null一样），如果用户希望插入的值为0（不改变），该列又是自增长的，那么这个选项就有用了。
STRICT_TRANS_TABLES
在该模式下，如果一个值不能插入到一个事务表中，则中断当前的操作，对非事务表不做限制。（InnoDB默认事务表，MyISAM默认非事务表；MySQL事务表支持将批处理当做一个完整的任务统一提交或回滚，即对包含在事务中的多条语句要么全执行，要么全部不执行。非事务表则不支持此种操作，批处理中的语句如果遇到错误，在错误前的语句执行成功，之后的则不执行；MySQL事务表有表锁与行锁非事务表则只有表锁）
NO_ZERO_IN_DATE
在严格模式下，不允许日期和月份为零
NO_ZERO_DATE
设置该值，mysql数据库不允许插入零日期，插入零日期会抛出错误而不是警告。
ERROR_FOR_DIVISION_BY_ZERO
在INSERT或UPDATE过程中，如果数据被零除，则产生错误而非警告。如 果未给出该模式，那么数据被零除时MySQL返回NULL
NO_AUTO_CREATE_USER
禁止GRANT创建密码为空的用户
NO_ENGINE_SUBSTITUTION
如果需要的存储引擎被禁用或未编译，那么抛出错误。不设置此值时，用默认的存储引擎替代，并抛出一个异常
PIPES_AS_CONCAT
将”||”视为字符串的连接操作符而非或运算符，这和Oracle数据库是一样的，也和字符串的拼接函数Concat相类似
ANSI_QUOTES
启用ANSI_QUOTES后，不能用双引号来引用字符串，因为它被解释为识别符
3、测试
本地起一个数据库，先查看sql_mode模式：
mysql> select @@global.sql_mode;
+--------------------------------------------+
| @@global.sql_mode |
+--------------------------------------------+
| STRICT_TRANS_TABLES,NO_ENGINE_SUBSTITUTION |
+--------------------------------------------+
1 row in set (0.00 sec)
mysql> select @@session.sql_mode;
+--------------------------------------------+
| @@session.sql_mode |
+--------------------------------------------+
| STRICT_TRANS_TABLES,NO_ENGINE_SUBSTITUTION |
+--------------------------------------------+
1 row in set (0.00 sec)
创建一个测试的表：
mysql> CREATE TABLE IF NOT EXISTS `demo`(
-> `id` INT UNSIGNED AUTO_INCREMENT,
-> `rank` VARCHAR(100) NOT NULL,
-> `name` VARCHAR(40) NOT NULL,
-> `gender` TINYINT NOT NULL,
-> PRIMARY KEY ( `id` )
-> )ENGINE=InnoDB DEFAULT CHARSET=utf8;
Query OK, 0 rows affected (0.02 sec)
mysql>
mysql> show tables;
+----------------+
| Tables_in_test |
+----------------+
| demo |
+----------------+
1 row in set (0.00 sec)
mysql> desc demo;
+--------+------------------+------+-----+---------+------------
| Field | Type | Null | Key | Default | Extra
+--------+------------------+------+-----+---------+------------
| id | int(10) unsigned | NO | PRI | NULL | auto_increm
| rank | varchar(100) | NO | | NULL |
| name | varchar(40) | NO | | NULL |
| gender | tinyint(4) | NO | | NULL |
+--------+------------------+------+-----+---------+------------
4 rows in set (0.01 sec) 插入测试数据：
mysql> insert into demo values(1, 'A', 'coderaction1', '20');
Query OK, 1 row affected (0.01 sec)
mysql> insert into demo values(2, 'B', 'coderaction2', '21');
Query OK, 1 row affected (0.00 sec)
mysql> insert into demo values(3, 'A', 'coderaction3', '22');
Query OK, 1 row affected (0.00 sec)
mysql> insert into demo values(4, 'C', 'coderaction4', '23');
Query OK, 1 row affected (0.00 sec)
mysql> insert into demo values(5, 'A', 'coderaction5', '21');
Query OK, 1 row affected (0.00 sec)
mysql> insert into demo values(6, 'C', 'coderaction6', '28');
Query OK, 1 row affected (0.01 sec)
mysql>
mysql> select * from demo;
+----+------+--------------+--------+
| id | rank | name | gender |
+----+------+--------------+--------+
| 1 | A | coderaction1 | 20 |
| 2 | B | coderaction2 | 21 |
| 3 | A | coderaction3 | 22 |
| 4 | C | coderaction4 | 23 |
| 5 | A | coderaction5 | 21 |
| 6 | C | coderaction6 | 28 |
+----+------+--------------+--------+
6 rows in set (0.00 sec) 分别执行以下sql命令：
mysql> select count(id) from demo order by rank;
+-----------+
| count(id) |
+-----------+
| 6 |
+-----------+
1 row in set (0.01 sec)
mysql> select count(id) from demo group by rank;
+-----------+
| count(id) |
+-----------+
| 3 |
| 1 |
| 2 |
+-----------+
3 rows in set (0.00 sec)
mysql> select count(rank),id from demo group by rank;
+-------------+----+
| count(rank) | id |
+-------------+----+
| 3 | 1 |
| 1 | 2 |
| 2 | 4 |
+-------------+----+
3 rows in set (0.00 sec)
mysql> select count(rank),id from demo group by id;
+-------------+----+
| count(rank) | id |
+-------------+----+
| 1 | 1 |
| 1 | 2 |
| 1 | 3 |
| 1 | 4 |
| 1 | 5 |
| 1 | 6 |
+-------------+----+
6 rows in set (0.00 sec)
mysql> 可以看到上面四个sql都执行成功。
修改sql_mode，临时修改sql_mode方式有两种，一种是设置当前会话连接的session级别的sql_mode，另一个是global级别的sql_mode。
session级别
先来看看session级别的sql_mode，设置方式有两种：
mysql> set session sql_mode='ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION';
Query OK, 0 rows affected (0.00 sec)
mysql> set @@session.sql_mode='ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION';
Query OK, 0 rows affected (0.00 sec)
mysql> select @@session.sql_mode;
+-------------------------------------------------------------------------------------------------------------------------------------------+
| @@session.sql_mode |
+-------------------------------------------------------------------------------------------------------------------------------------------+
| ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION |
+-------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)设置session级别sql_mode，当前session级别查询到新的，下次重连后失效。
global级别
再看看global级别的sql_mode，设置方式有两种：
mysql> set @@global.sql_mode='STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION';
Query OK, 0 rows affected (0.00 sec)
mysql> set global sql_mode='STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION';
Query OK, 0 rows affected (0.00 sec)
mysql> select @@global.sql_mode;
+------------------------------------------------------------------------------------------------------------------------+
| @@global.sql_mode |
+------------------------------------------------------------------------------------------------------------------------+
| STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION |
+------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)
设置global级别sql_mode，当前session级别查询到还是旧的，所以执行命令时，还是按照旧配置。下次重连后利用新配置。
当我们设置完上面session级别的sql_mode，在其中加ONLY_FULL_GROUP_BY后，执行测试sql语句报错：
mysql> select count(rank),id from demo group by rank;
ERROR 1055 (42000): Expression #2 of SELECT list is not in GROUP BY clause and contains nonaggregated column 'test.demo.id' which is not functionally dependen
t on columns in GROUP BY clause; this is incompatible with sql_mode=only_full_group_by
mysql> select count(rank),id from demo group by id;
+-------------+----+
| count(rank) | id |
+-------------+----+
| 1 | 1 |
| 1 | 2 |
| 1 | 3 |
| 1 | 4 |
| 1 | 5 |
| 1 | 6 |
+-------------+----+
6 rows in set (0.00 sec) 这也验证了：SELECT后面接的列必须被GROUP BY后面接的列所包含。
注意：通过session和global设置临时生效的，即当mysql重启后，都会失效。需要在mysql启动配置文件中默认设置。
4、解决办法
除了上面测试时用到的临时解决的两种方法。要想mysql重启后依然生效，需要在mysql的配置文件，一般是my.cnf中的[mysqld]下面加sql_mode配置。因为我使用的是k8s部署的mysql，镜像安装和在宿主机上通过软件包安装有一定差别。但最终还是更改的my.cnf。
kubectl exec -ti mysql-75797cf796-84rdl bash
root@mysql-75797cf796-84rdl:/#
root@mysql-75797cf796-84rdl:/# cat /etc/mysql/my.cnf
Copyright (c) 2016, Oracle and/or its affiliates. All rights reserved.
.....
!includedir /etc/mysql/conf.d/
!includedir /etc/mysql/mysql.conf.d/
在这里插入图片描述
可以看到这里包含了两个目录下的文件，查看一下，mysql.conf.d下，发现有我们需要更改的文件
cat /etc/mysql/mysql.conf.d/mysqld.cnf
查看并将该文件用kubectl cp命令拷贝到宿主机上，修改后最终要挂载进入pod里。
kubectl cp default/mysql-75797cf796-84rdl:/etc/mysql/mysql.conf.d/mysqld.cnf /data/blog-solo/mysql-config/mysqld.cnf
修改后文件如下，主要关注sql_mode
root@mysql-75797cf796-84rdl:/# cd /etc/mysql/mysql.conf.d/
root@mysql-75797cf796-84rdl:/etc/mysql/mysql.conf.d# ls -l
total 4
-rw-r--r-- 1 root root 1671 Oct 26 11:40 mysqld.cnf
root@mysql-75797cf796-84rdl:/etc/mysql/mysql.conf.d# cat mysqld.cnf
Copyright (c) 2014, 2016, Oracle and/or its affiliates. All rights reserved.
...
[mysqld]
pid-file = /var/run/mysqld/mysqld.pid
socket = /var/run/mysqld/mysqld.sock
datadir = /var/lib/mysql
sql_mode = STRICT_TRANS_TABLES,NO_ENGINE_SUBSTITUTION
log-error = /var/log/mysql/error.log
By default we only accept connections from localhost
bind-address = 127.0.0.1
Disabling symbolic-links is recommended to prevent assorted security risks
symbolic-links=0
root@mysql-75797cf796-84rdl:/etc/mysql/mysql.conf.d#
最后修改mysql-deployment：
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
name: mysql
spec:
replicas: 1
template:
metadata:
labels:
name: mysql
spec:
containers:
- name: mysql
image: mysql:5.7.28
imagePullPolicy: IfNotPresent
ports:
- containerPort: 3306
env:
- name: MYSQL_ROOT_PASSWORD
value: "password"
volumeMounts:
- name: mysql-config
mountPath: /etc/mysql/mysql.conf.d
- name: mysql-data
mountPath: /var/lib/mysql
volumes:
- name: mysql-config
hostPath:
path: /data/blog-solo/mysql-config/
- name: mysql-data
hostPath:
path: /data/blog-solo/mysql-data/注意要把配置文件和数据都挂载到宿主机上，否则pod重启后就会丢失配置和数据。
