准备条件：
设置从库只读
SET global read_only = ON;
创建数据跨丽娜姐账户，并分配普通权限
CREATE USER 'readonly'@'%' IDENTIFIED BY '123456';
GRANT SELECT,INSERT,UPDATE,delete ON *.* TO 'readonly'@'%';
FLUSH PRIVILEGES;
或
grant SELECT,INSERT,UPDATE,delete ON *.* TO 'readonly'@'%' identified BY '123456';
