1，mysql中文显示为？解决办法
show variables like 'character_set_%';
show variables like 'collation_%';
character_set_database 和 character_set_server 应该为utf8，collation_database 和 collation_server应该为utf8_general_ci.
如果不一样需要修改/etc/my.cnf
首先关闭数据库以及断开数据库服务
/etc/init.d/mysqld stop
service mysqld stop
打开my.cnf后，在文件内的[mysqld]下增加如下两行设置：
charcter_set_server=utf8
init_connect='SET NAMES utf8'
保存退出
重新启动数据库服务
/etc/init.d/mysqld start
service mysqld start
2,
修改数据库编码格式
alter database <数据库名> character set utf8；
修改数据表编码格式
alter table <表名> character set utf8；
修改字段编码格式
alter table <表名> change <字段名> <字段名> <类型> character set utf8;
例如：alter table user change username username text character set utf8 not null;
3,
Establishing SSL connection without server's identity verification is not recommended. According to MySQL 5.5.45+, 5.6.26+ and 5.7.6+ requirements SSL connection must be established by default if explicit option isn't set. For compliance with existing applications not using SSL the verifyServerCertificate property is set to 'false'. You need either to explicitly disable SSL by setting useSSL=false, or set useSSL=true and provide truststore for server certificate verification.
查看sql_mode
select @@sql_mode
去掉ONLY_FULL_GROUP_BY，重新设置值。
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 ';
4，
Error Code:1175. You are using safe update mode and you tried to update a table without a WHERE that uses a KEY column To disable safe mode, toggle the option in Preferences -> SQL Queries and reconnect
set SQL_SAFE_UPDATES=0;