PDM(Physical DataModel)that is, physical data model,It details the physical realization of the database, Here we will specifically consider the details of physical implementation,including data storage structure,Can be modified byPDM to adapt to performance/Physical constraints.
PDM< The main function of span lang="zh-CN" style="font-family:宋体"> is:
1Draw the physics of the data graphically Organization structure,
2Create and modify the database;
3define referential integrity ;
4 Generate extended attributes;
5Can be reproduced by reverse engineeringCDM.
is in the computer room charging system When I went through the document, when I wrote the detailed design specification, it asked for the physical data model of the system’s database, so I took the computer room charging system as an example, and tried to usePowerDesigner12.5 to draw the computer room charging systemPDM, the following is the computer room charging system I drew PDM: span>
UnderstandPDM The people at can definitely see that the pictures I drew are not complete, and there are many mistakes because I just try to draw them. The database was not designed by me when I was doing the first system, and I didn’t use it at that time. So I used the database given in the data. The figure above is also a description of that database, so I said that I drew the picture based on the database that has been created. Based on this, it was found that there were too many defects in the original database. Obviously, the data redundancy is very serious.
is followed by drawing using Object-oriented design thinking, the existing database at that time was not designed in an object-oriented way at all, so the entity of the original database was abstracted and analyzed, and the nondescript above was drawn.PDM. Although the knowledge of the database has been studied, I feel that it is not enough to use and practice flexibly. In the follow-up study, I should go back and review the database.
Personally think PDMThe biggest charm is that it can directly Generate the script to create the database, but my attempt has not been successful. The reason must be the design of the database andPDMPDM span>There is a problem with the drawing, which needs further study…