table of Contents
Theoretical stuff is the most disgusting, in line with the principle of exam-taking, put a few related links
Normalization and paradigm
This part of the direct look at the others written database of three paradigms
look at some functions depend entirely dependent on the function, the transfer function dependent on the difference between three paradigms
Find closure
Look at the database closure and search
Pattern decomposition
Three definitions of model decomposition:
the decomposition of a model is diverse, but the model generated after decomposition should be equivalent to the meta-model. People observe the problem from different angles, and there are three different types of "equivalence". Definition:
- Decomposition has lossless connectivity
- Decomposition to maintain the functional dependency
- Decomposition must not only maintain functional dependency, but also have lossless connectivity
1) If you want to maintain functional dependence, then the mode decomposition can always reach 3NF , but not necessarily BCNF
2) If you want to maintain functional dependence and have lossless connectivity, you can reach 3NF , but not BCNF
3) If decomposition is required With lossless connectivity, it must be 4NF
Related topics:
look at pattern decomposition,
look at the minimum functional dependency set,
look at how to find candidate codes
After studying this chapter, I found that I am not so disgusted with this kind of partial theory. I also found that this knowledge is still quite important for designing an efficient database.