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This article mainly introduces "what is the performance of the integrity constraints of database design". In the daily operation, I believe that many people have doubts about the integrity constraints of database design. I have consulted all kinds of materials and sorted out simple and easy-to-use operation methods. I hope it will be helpful for you to answer the doubts about "what is the performance of integrity constraints in database design?" Next, please follow the editor to study!

What are the aspects of the integrity constraints of database design? The following four aspects are mainly written:

1. Domain integrity: columns in a database table must meet a specific data type or constraint. Among them, the constraint includes the range of value, precision and so on. Using Check to implement constraints, in the database design tool, when defining the value range of a field, there is a Check button that defines the value city of the field.

2. Referential integrity: define the reference rules between the outer code and the main code. It is realized by competition, FK and table-level triggers. The principle rule is that if the attribute (or attribute group) f is the outer code of the basic relation r, which corresponds to the main code ks of the basic relation s (the basic relation r and s are not necessarily different relations), then the value of each tuple in r must be: or take a null value (each attribute value of f is null) or equal to the main code value of a tuple in s.

3. Entity integrity rules (entityintegrity): if attribute an is the primary attribute of the basic relation r, attribute a cannot be null. Because entity integrity rules are for basic relationships. A basic table usually corresponds to a set of entities or many-to-many relationships in the real world. Entities and the relationships between entities in the real world are distinguishable, that is, they have some kind of unique identity, and the relational model of database design must comply with the rules of entity integrity.

4. User-defined integrity: user-defined integrity is a constraint for a specific relational database, reflecting the semantic requirements that the data involved in a specific application must meet. Relational models should provide mechanisms for defining and verifying such integrity so that they can be handled in a unified and systematic way, rather than by the application. It is some business rules that are implemented with stored procedures and triggers.

At this point, the study of "what are the integrity constraints of database design" is over. I hope to be able to solve everyone's doubts. The collocation of theory and practice can better help you learn, go and try it! If you want to continue to learn more related knowledge, please continue to follow the website, the editor will continue to work hard to bring you more practical articles!

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