Bonus Weak association patterns

[ishanijerin1]

Considering the relationship between the table and chairs in a dining set, a single table would have one and about four chairs. However, another dining set may have a combination of a smaller table and two chairs. This information about two or four items is not managed as an attribute of the product itself, but is managed by an intermediary.

The role of the intermediary is to create a relationship without polluting the product information of either party. Both products can call the intermediary at any time, so they can treat the information as if it were their own.


When a product is deleted, it is important to consider whether the intermediary should also be deleted. In the case of a set product, it is normal to delete the intermediary when the set product is deleted. When the intermediary is no longer there, the relationship between these why you need this database products will no longer exist.

In other words, the deal is broken off.


In the data model, this is expressed as an "intermediate table."


This is a relationship pattern in which only the ID information of the related data is set in the attributes when the related data is not managed in PIM . This relationship pattern cannot be defined with one-way, two-way, or intermediate relationship patterns, and is only used when it is assumed that the data will never be deleted. Care must be taken with this relationship pattern, as it will not cause inconsistencies in the system even if the related destination is deleted.

It's like quitting a social networking site without realizing it.


Either way, it is a tenuous connection, with only the ID being known.

Some people say that's a good thing, but from past experience, it tends to disappear.