Database design Ideas

1, it is best not to use the self-increment attribute field as the primary key and the Child Table Association. System migration and data recovery are not facilitated. The mapping relationship of external statistic system is lost. 、

2, the length of the data line should not exceed 8020 bytes, if more than this length, the data in the physical page will occupy two lines resulting in storage fragmentation, reduce query efficiency.

3. The ability to select numeric types instead of string types (phone numbers) with fields of numeric type, which reduces the performance of queries and connections, and increases storage overhead. This is because the engine is processing the query and connecting back to each character in a string by comparison, and for a digital type it only needs to be compared once.

4, for the immutable character type char and the variable character type varchar are 8000 bytes, char query fast, but consumes storage space, varchar query is relatively slow but save storage space. In the design of the field can be flexible choice, such as user name, password, such as the length of the field can be selected char, for the comment, such as the length of a large variety of fields can choose varchar.

5, the length of the field in the maximum possible to meet the needs of the premise, should be set as short as possible, so as to improve the efficiency of the query, but also in the establishment of the index can reduce the consumption of resources.