lsp association

student score of 1 to Score1, when I add a student information of 2 to the Student1 table, it is added unsuccessfully, because there is no association, unless there is a student score of 2 in Score1. Only in this way can there be referential effect, so the referential integrity is ensured. Add: What is from the table, what is the main table, STUDENT1 has the statement CONSTRAINT fk_stu_id_score1 FOREIGN KEY (stu_id) REFERENCES score1 (stu_id) means t

IosCoreData framework is used to add, delete, modify, and query context data, association between tables, 1-to-many, 1-to-1, predicate query, and multi-Table connection. -(Void) viewDidLoad {[super viewDidLoad]; [self _ creatTable]; // insert data // [self _ query]; // query data // KVC is overbearing, even if readonly can be assigned a value through kvc, kvo essence // Book * book = [[Book alloc] init]; // book. name = @ "book1"; // [book setValue:

The relationships defined by UML are: generalization, implementation, dependency, association, aggregation, and combination. The closeness of these six relationships is enhanced in turn.1. Generalization Concept:Generalization isGeneral and Special,General and specificDescription of the relationship between them. The detailed description is based on the general description and is extended. In a program, it is implemented through an inherited class. Fo

Association rule association rule mining is one of the many "rule-based" data mining methods. The basic theory of Association Rules (assuming that the reader knows) is not described here in detail, the following describes the algorithm design. The main idea of the Apriori algorithm: 1. The candidate item set is constructed based on "the subset of a frequent ite

Hibernate-one-to-multiple unidirectional Association ing and hibernate ing [Hibernate]-about one-to-multiple unidirectional Association ing One-to-Multiple Association ing based on foreign keys! One-to-multiple, Group for Person, a Group can have multiple people! OK? Hibernate mainly has two Configuration Methods: Annotations and XML! The following describes h

Approach one: Nested results: Use nested result mappings to process subsets of duplicate federated results, encapsulate data from a table query (removing duplicate data)SELECT * from class C,teacher t WHERE c.tid = T.tid and C.cid=#{id}Method Two: Nested query, by executing another SQL mapping statement to return the expected complex typeSELECT * from class C,teacher t WHERE c.tid = T.tid and C.cid=#{id}SELECT t.tid ID, t.tname name from teacher t WHERE T.tid = #{id}//Use the TID found above

This article mainly introduces the method of Yii2.0 Table Association query, and analyzes the implementation method and related use skill of the association query in Yii, and the friend can refer to it. This article describes the method of Yii2.0 Table Association query. Share to everyone for your reference, as follows: You can use ActiveRecord to correlate quer

When we do database design, the most annoying is the relationship between the various tables, the correlation relationship is: one-to-many, many-to-a, one-on, and there is one-way and two-way difference.　　1. Bidirectional one-to-many and multi-pair mapping: since the two-way, then is the same kind of: two-way one-to-many relationship, there must be a relationship between the maintenance side, in the JPA specification, requires the many side as the maintenance side of the relationship (owner side

Sixth Hibernate Association Mappingsfirst, The knowledge points of this chapter are divided into 2 parts:1. relationship: one-way many-to-one relationship, two-way-to-multi-association relationship (with a pair of multi-related relationships), Many-to-many Association relationships2. Lazy loading: class-level load policy, one-to-many-load policy, multi-pair loadi

Unique FOREIGN Key Association: A Foreign Key association, which is intended for many-to-one configurations, but can also be used to represent a to-do relationship if a unique restriction is added;One, one-way association mappingsOne (Maintenance: person) [' Multi-terminal ']ToOne (non-maintenance: idcard) [' one End ']Two, two-way

The basic idea of object-oriented programming is to use a program to simulate the world, which makes its various fundamental features very user-friendly, such as encapsulation, inheritance, polymorphism, etc, the virtual function is the main implementation of polymorphism in c ++. To achieve polymorphism, the c ++ compiler also revolutionizes Dynamic Association (or late bundling. Virtual functions are also the key to mfc programming. There are two ma

will be deleted, and then the user of the corresponding group can be deleted, because @manytoone (Cascade={cascadetype.all}) is set.Delete both user and groupThree ways to avoid all deletions:1. Remove @manytoone (Cascade={cascadetype.all}) settings;2. Direct write HQL statement execution delete;@Test Public void Testdeleteuser () { testsavegroup (); = sessionfactory.getcurrentsession (); S.begintransaction (); S.createquery ("Delete fro

association, it is best to write on Mappedby, two tables have a foreign key is enough. Many-to-one one-way association everyone has a lot of dreams, but every dream belongs to a specific person.Let's start with how the Java code is implemented in the database.The two tables above, one is person, the inside is Id,nameThen Dream table, an ID, a description.So which table are their foreign keys on?In the drea

(Student2);Classes Classes = new Classes ();Classes. SetName("Tgb--9");Classes. Setstudents(students);Session. Save(classes);Tx. Commit();}catch (Exception e) {E. Printstacktrace();if (tx! = null) {TX. Rollback();}}finally{Hibernateutils. CloseSession(session);} }(Note: The code implementation of calling Hibernateutils in the program can be consulted: Hibernate (four)--association map (many to one))Execute the Print SQL statement as follows:hiberna

UML has four relationships: dependency, association, generalization, and implementation. (1) dependency is the semantic relationship between two things. Changes in one thing (independent thing) will affect the semantics of the other thing (dependent thing. On the graph, draw a dependency into a dotted line that may have a direction. (2) Association is a structural relationship that describes a group of li

In UML, the relationships between classes can be divided into dependency, association, aggregation, and combination. These four types of relationships can be seen as associations in a sense. from dependency to combination, their association intensity is from weak to strong. Dependency is the weakest association between classes. In reality, Class B is used in a

Next, this time, only the nested results, the same as the last three sheetsThe last time I forgot to introduce resultmap, fill in:Resultmap Conceptual View When the constructor– class is instantiated, it is used to inject the result into the constructor method Idarg–id parameters; Marking results as IDs can help improve overall performance A common result of arg– injection into the construction method ID – an ID result; Marking results as IDs can help improve overall perform

Example of Cgridview association table search sorting method in Yii, Yiicgridview In this paper, we describe the Cgridview association table search Ordering method in Yii. Share to everyone for your reference. The implementation method is as follows: In Yii Cgridview Association table Search Sort implementation method is a bit complicated, today read a foreigner

One-to-one association ing (using a unique foreign key + one-way) Hibernate one-to-one unique foreign key Association ing (one-way Association person ----> idcard) A unique foreign key Association ing is a special case of multi-to-one association ing. You can use the P

One-to-one association ing (bidirectional) To implement one-to-one bidirectional Association ing, let's take the person and ID card as an example to understand: Hibernate one-to-one primary key Association ing (two-way Association person Step 1: first, establish the object relation class of the person and ID card: