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has no children), but must have a foreign key (because it has a father ).The Design of primary keys and Foreign keys plays an important role in the design of global databases. After the design of the global database was completed, an American database
it has no children), but you must have a foreign key (because it has a father ).The Design of primary keys and Foreign keys plays an important role in the design of global databases. After the design of the global database is complete Database
Tags: mysql database stored procedure trigger MySQL database permissions database design three major paradigmsA. MySQL stored procedure1. Concept: SQL statement with logic, there is no condition in the previous SQL statement, no loop, the stored procedure with the Process Control statements.2. Features:(1) Execution ef
When it comes to databases, I don't think we have to talk about the data structure first. In 1996, when I first went to college to study computer programming, the teacher told us: ComputerProgram= Data Structure +Algorithm. Although the current development of programs has gradually transitioned from process-oriented to object-oriented, I strongly agree with the formula that the teacher told us eight years ago: computer programs = data structures + algorithms. The first thing to do in object-orie
eliminated. The solution is to add a third entity between the two. In this way, the original multi-to-many relationship is now two one-to-many relationships. The attributes of the original two entities should be reasonably allocated to the three entities. The third entity here is essentially a complex relationship, which corresponds to a basic table. Generally, database design tools cannot identify many-to
Database Design Principles 1. The relationship between the original document and the object can be one-to-one, one-to-many, and many-to-many. In general, they are a one-to-one relationship: an original document corresponds to only one entity. In special circumstances, they may be one-to-many or many-to-one relationships, that is, an original document corresponds to multiple entities, or multiple original do
allow redundancy. 6. Be good at identifying and correctly handling many-to-many relationships If there is a many-to-many relationship between two entities, this relationship should be eliminated. The solution is to add a third entity between the two. In this way, the original multi-to-many relationship is now two one-to-many relationships. The attributes of the original two entities should be reasonably allocated to the three entities. The third entity here is essentially a complex relation
relationship between the two entities. The solution is to add a third entity between the two. Thus, the original oneA many-to-many relationship now becomes two one-to-many relationships. To properly assign the original two entity's attributes to three entities. Here's the third oneAn entity is, in essence, a more complex relationship that corresponds to a basic table. In general, database design tools do n
a many-to-many relationship between the two entities. The solution is to add a third entity between the two. In this way, the original a many-to-many relationship, now becomes two one-to-many relationship. To properly assign the original two entity's attributes to three entities. The third entity here is essentially a more complex relationship that corresponds to a basic table. Generally speaking, the database de
Typically, there are two ways to judge whether a database is designed to be a comparison specification. One is to see if you have a large number of narrow tables, and the second is whether the number of wide tables is enough. If these two conditions are met, it can be explained that the standard level of the database is still relatively high. This, of course, is a two-a-kind indicator. In order to meet the
, to improve operational efficiency, we must lower the paradigm standard and properly retain redundant data. The specific approach is to follow the third paradigm in conceptual data model design, and to reduce the paradigm standard to be considered in physical data model design. Reducing the paradigm is to add fields and allow redundancy. 6. Be good at identifying and correctly handling many-to-many relatio
no child), but must have a foreign key (because it has a parent ). The Design of primary keys and Foreign keys plays an important role in the design of global databases. After the design of the global database was completed, an American database
child), but must have a foreign key (because it has a parent ).The Design of primary keys and Foreign keys plays an important role in the design of global databases. After the design of the global database was completed, an American database
no child), but must have a foreign key (because it has a parent ). The Design of primary keys and Foreign keys plays an important role in the design of global databases. After the design of the global database was completed, an American database
Link Attribute Tuples Insertion exception: when inserting data, the data cannot be inserted into the database, and the relational database cannot be operated, that is, the insertion exception. Deletion exception: when unnecessary information in a link is deleted, the information that should not be deleted is also deleted, that is, the deletion exception. Update exception: when updating a
and multi-site update functions, with location transparency and venue autonomy. It provides a global database name and supports remote process calls. Development Tools The Development kits provided by Oracle are developer/2000, designer/2000, discover/2000, and Oracle office. They cover all aspects from modeling, analysis, design to implementation. Developer/2000 includes: Oracle Forms is used to quickly g
has no child), but must have a foreign key (because it has a parent ).The Design of primary keys and Foreign keys plays an important role in the design of global databases. After the design of the global database was completed, an American database
Before designing a database1. Test the existing environmentWhen designing a new database, you should not only carefully study the business needs, but also examine the existing system. Most DatabasesProjects are not built from scratch. Normally, there will always be existing systems within the Organization to meet specific needs (there may be no realAutomatically calculated ). Obviously, the existing system is not perfect, otherwise you do not have to
no child), but must have a foreign key (because it has a parent ). The Design of primary keys and Foreign keys plays an important role in the design of global databases. After the design of the global database was completed, an American database
button on the page 3, the permission can be "visible", can be "read-only" or "Available " ( such as a button can be clicked ) is actually the WHO, what, how problem So the six tables mentioned above can actually design a table: IV, example description Here is an example of a design description. "User, role on page is permission to use" Detailed design: 1,
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