A: static and dynamic separation
Explanation: do the best separation of static tables and dynamic tables. Here to explain the meaning of static tables and dynamic tables, static table: some fixed storage resources, such as city / region name / country (be sure to use a static table cache). Dynamic Table: Some frequently modified table
II: About Null value
Explanation: Try not to have a null value, has null value, the time of indexing time database queries longer, wasting more time! You can set a default value when construction of the table!