1, the primary key is an ID of the table, which mainly plays the role of identifying a data. For example, if the book list in the library has several items such as ID, librarian, author, publication date and publisher, and the ID is uniquely identifiable, then the ID is the primary key. A foreign key is a data item associated with a book table in other tables. For example, the detailed information table of publishing house includes several items such as publishing house name, publishing house address and publishing house history, all of which point to the book table, so the publishing house name in the book table is the foreign key pointing to the publishing house table.

3. The primary key is set according to its uniqueness.

Foreign keys are set according to the relationship between tables.

4. The link between the interface and the database can call the database language through the local background of the interface, such as connect to db.

Some programming languages need to be configured in the compiler, such as. Net.

5. A good pattern design method should conform to three principles: (1) expressiveness (2) separability (3) minimum redundancy.

6. As mentioned above, it can be accessed directly in the background. Of course, if the database is built in advance, the encapsulated database access classes are usually called for access, and the compiler should integrate these classes.

7. Software development is to write demand analysis first, then overall design, detailed design, start programming, write test cases after completion, and finally complete test delivery and post-delivery training.

8.E-R diagram, also known as entity relationship diagram, provides a method to express entity types, attributes and relationships, and is used to describe the conceptual model of the real world.

E-R method is the abbreviation of "entity relationship method". It is an effective method to describe the conceptual structure model of the real world. It is a way to express the conceptual model. Entity types are represented by rectangles, and entity names are written in rectangular boxes. The attributes of entities are represented by ellipsis, and connected with corresponding entities by undirected edges. Use a diamond to indicate the connection between entity types, write down the contact name in the diamond box, connect the entity types with undirected edges respectively, and mark the connection type (1: 1, 1:n or m:n) beside the undirected edges.

Hand, I hope I can help you