Database design bald head Artoria ---- Pan Liang
The last few weeks we Artoria group designed a digital museum databases couplets, and the Chinese couplets associations and database consolidation.
The following tips and ideas we talk about database design.
First, we should analyze the document in accordance with the needs doing before, one needs to think against the database should keep what data to complete these requirements, should be how to save the data. As you demand a more complete analysis, not only database to store the data to understand what the whole program in general design ideas also clear.
We started from the perspective of minimizing redundancy to design a database to correlate the number of optional attributes to create a new table and main table.
For example, we will introduce Couplets dispensable, appreciation, author information are opening a new table.
However, when the database design review, while the teacher suggested that we do not use this structure to make use of redundancy, so that not only the simple design of the database, after a simple operation of the database, the efficiency of the program will be higher, but with the redundant data now the disk capacity has been greatly improved it is not a big problem. The use of redundant even avoid a lot of table operation (cumbersome and inefficient).
Finally, we made such:
All the non-essential data into a table, a table and some may be not satisfied three paradigms (such as whether the members here and the respective associations is clearly redundant), but does not meet the three paradigms database is not necessarily bad and sometimes in order to improve operational efficiency, it must reduce the standard paradigm, appropriate to retain redundant data. Specifically: physical data model designed to comply with the third paradigm in conceptual data model design, reduce the standard paradigm of work into consideration. Paradigm is reduced to increase the field, allow for redundancy, in order to achieve the object space for time.
We in teams to design a database, we unified a certain field what type, after the time of the merger on the simple, but we couplets Digital Museum Association and the Chinese couplets another group with the same database, so we faced with the question of integration of the database, and the combined, their types and our completely different type, even also some type of internal disunity, we re-group database rectification + merge almost equal to re-write it again. . .
Therefore, before the block design database, you must first confirm a standard.
In the design of the database, named among the different entities must distinguish, if the name confused, powerDesigner automatically associated attribute of the same name, then all kinds of unexpected errors occur, we design a database at the beginning I found a change in the attribute table, the attribute of another table can change to follow. . . Named because of the problem.
When CDM is generated PDM, many relationships that will a party primary key as a foreign key that is inserted into a multi-party; many relationships generate a new table, the two sides of the primary key as the entire primary key; one relationship you need to first determine the main from the relationship, and then as many.
This is the ultimate database after we merged, or not easy ~
