access relationships

Note: All essays on this blog are original on cnblogs by eaglefish. You are welcome to reprint them, but please indicate the source.CDM is the first model created by most developers when using PD, and is also the highest abstraction of the entire database design. CDM is built on the traditional ERTU model theory. ERTU has three main elements: solid shape, attributes, and relationships. The entity type corresponds to the entity in the CDM, and the attr

In addition to the inheritance relationship between objects and objects, there is also an association: including a pair of more than one or one pairs of many pairs of one and many pairs, because these relationships in the Kodo EJB implementation of the principle is basically similar, so this article mainly on a pair of related relations in depth, At the same time, through simple examples of analysis and practice in detail how to use the annotations pr

table in the parent table class by means of the relationship () method (Base): __tablename__ = ' children ' id = Column (integer, primary_key=true) parent_id = Column (Integer, ForeignKey (' parent.id ')) # in the child table class through the foreign key (foreign key) refers to the reference field of the parent table to establish a bidirectional relationship in One-to-many, where the "reverse" side are a many to one, at a one-to-many relationship in which two-way

Tags: img build field number parent multi-to-one ONS int course1 table and table three relationships 1.1 One-to-one relations Example: A husband who corresponds to a wife, a wife to a husband 1.2 One-to-many relationships Example: A person can have more than one car, asking for a search for all the vehicles owned by someone Analysis: This can actually be a table, but because a person can have more than one

Label:Problem Description: For example, there is a team table in the relational database, a user table, the two are many-to-many relationships, that is, a team can have multiple user, a user may belong to more than one team, how does such a relationship in MongoDB storage?If it is a pair of more, I know can be nested, but do not know how to deal with many-to-many relationships, please advise. "From the moun

target device; it's important to consider this early in the design process to ensure that the application can adapt to its environment. In our example application, we want to enable users to view, save, and share categorized stories and photos. Below is an exhaustive list of screens that covers these use cases. Home or "launchpad" screen for accessing stories and photosList of categoriesList of news stories for a given categoryStory detail view (from which we can save and share)List of photos,

There are two table rule tables and group tables: tb_rules and tb_group. These two tables are in the auth permission. Obviously they are multi-to-many relationships. A rule can belong to multiple groups, A group can have multiple rules. In principle, there should be an association table tb_group_rules (group_id, rule_id )... there are two table rule tables and group tables: tb_rules, tb_group This isauthThe two tables in the permission are obviousl

What are the associated models and multi-table queries? What are their relationships? What are the associated models and multi-table queries? What are their relationships? Reply content: What are the associated models and multi-table queries? What are their relationships? The association model is an automatically maintained table-to-table relationship def

In hibernate, there are usually two kinds of configuration object relationship mapping relationship, one is based on XML, the other is based on annotation annotation, cooked words, radish green vegetables, can have love, everyone has their favorite configuration, I tried these two ways, Find the way to use annotation can be more brief, so here is a simple record under the annotation to configure the various mapping relationships, after hibernate4 has

Transferred from:http://blog.csdn.net/tianhai110/article/details/6339565In UML class diagrams, the following relationships are common: generalization (generalization), implementation (realization), Association (association), Aggregation (Aggregation), composition (composition), dependency ( Dependency)1. generalization (generalization)Generalization relationship: An inheritance relationship that represents a general and special relationship that speci

relationship between the whole and the individual, that is, the relationship between the has-a, the whole and the individual can have their own life cycle, some can belong to more than one whole object, can also be shared for multiple whole objects. The aggregation and association relationships in the program are consistent and can only be differentiated from the semantic level;Presentation method: A solid arrow with a hollow diamond at the tail (or

The relationships between classes and classes are:1. Related relations;2, the combination of relations;3, the aggregation relationship;4, the dependence relationship;5, inheritance relations;6, the realization of the relationship;Among them, the combination relation and the aggregation relation are the special correlation relations.Association relationship:A->b a association B is a one-way association, if b->a, it forms two-way association;Semantics:

Read a book before, the introduction of hibernate in the time repeatedly stressed not easy to set a one-way relationshipThe reason for the explanation in the book is that it affects performance (the resulting SQL statements become more).one-way, many-to-1 Relationships foreign Key dependency: by following the @ManytoOne @CasCadeFirst persist from the table records, and then persist the main table record: when the main table does not have a correspondi

Requirement 1:Deploy SSH trust relationships in large quantities, deploy web-level trust relationships at the a file distributor at high volumeThe file Distributor is: 10.0.3.9 logon User: ZhangsanWeb Layer IP segment:10.0.3.10~10.0.3.60(1), please build Zhangsan users on the Web tier, and create a. SSH directory under the Zhangsan home(2) on the 3.9 server, the Zhangsan user creates the private key and pub

In UML class diagrams, the following relationships are common: generalization (generalization), implementation (realization), Association (association), Aggregation (Aggregation), composition (composition), dependency ( Dependency)1. generalization (generalization)Generalization relationship: An inheritance relationship that represents a general and special relationship that specifies how subclasses can characterize all the characteristics and behavio

From: http://gisattic.cnblogs.com/archive/2005/11/26/284922.html 1st: understanding how to "listen to people" is a prerequisite for the popularity of others. 2nd: only good at displaying "Real yourself" can attract others to their attention. 3rd: the key to the success or failure of first-time communication is a proper cold greeting. 4th: To win others' trust in yourself, you must first show it to others. 5th: Be careful not to be too close to others, maintain proper distance, and contri

UML class Diagram Relationships (generalization, inheritance, implementation, dependencies, associations, aggregations, combinations)In UML class diagrams, the following relationships are common: generalization (generalization), implementation (realization), Association (association), Aggregation (Aggregation), composition (composition), dependency ( Dependency)1. Generalization (generalization)Generalizati

dependency, a relationship that is not temporary, and generally long-term, in which the associated Class B appears in the association Class A in the form of a class attribute. It is also possible that the Association Class A refers to a global variable of type class B that is associated withPresentation method: solid arrow, Class A points to Class BPolymerizationConcept: A special case of the aggregation association, which is a strong correlation relationship. Aggregation is the relationship be

In UML class diagrams, the following relationships are common:Generalization (generalization), implementation (realization), Association (association), Aggregation (Aggregation), composition (composition), dependency (Dependency)1. generalization (generalization)Generalization relationship: An inheritance relationship that represents a general and special relationship that specifies how subclasses can characterize all the characteristics and behaviors

The full name of ORM is object/Relation Mapping, that is, object relationship ing. Since ORM is developed, it is inevitable to involve the relationship between objects. Through the abstraction of object-oriented ideas, we can define the relationships between objects as follows: One-to-one Multiple-to-one (one-to-multiple) Many-to-many We can easily create an enumeration for object