Mysql的权限问题以及flush privileges:

Mysql的权限分为以下四种：
    1.全局权限
        eg：grant all privileges on *.* to 'test'@'%' with grant option;
                revoke all privileges on *.* from 'test'@'%';
    2.db权限
        eg：grant all privileges on testdb.* to 'test'@'%' with grant option;
                revoke all privileges on testdb.* from 'test'@'%';
    3.表权限
        eg：grant all privileges on testdb.test0701 to 'test'@'%' with grant option;        
    4.列权限
        eg：grant select(id), insert(id,a) on testdb.test0702 to 'test'@'%' with grant option;