[DB] paradigm, db paradigm

[DB] paradigm, db paradigm

In my previous blog [DB] function dependency, I mainly explained what is function dependency and local and transfer dependency (FD ). When there is no FD, data redundancy is not possible in the Link. However, when the FD exists, data redundancy may exist in the link. How can this problem be eliminated? The answer is pattern decomposition. So what is it like? How can we measure the good and bad relationship patterns? The answer is Paradigm (NF )!

The types of NF are directly related to FD. The FD-based paradigm includes 1NF, 2NF, 3NF, BCNF, and 4NF. Next we will introduce it separately!

1NF

Each relational R in relational mode r has a single-value attribute.

2NF

Eliminate local dependency

3NF

Eliminate passing Dependencies

BCNF

In 3NF, the transmission dependency of the primary attribute on the candidate key is not excluded ,:

R is called BCNF mode only when no candidate key dependent on mode R is passed for each attribute.

4NF

4NF is a direct promotion of BCNF.

3NF VS BCNF

Non-primary attributes and all attributes

Bcnf vs 4NF

4NF is for multi-value dependency, and the attributes in relational r contain multi-value attributes.

Summary

1. 2NF, 3NF, and BCNF are all based on 1NF, and their premise is that the attribute of the relational r is a single value attribute.

2. 2NF has become history, and 3NF and BCNF are currently the most commonly used.

3. I finally understood the paradigm. I am very happy. It seems that if you want to understand it, you will not be able to solve it!

Paradigm trustworthiness

The paradigm word is huge, and it is less than that of taixue. Character Generator. They asked for leave to return to their hometown. Expression: "the next two years, when the return, will pass the honorable person ." The communist day. Later, the father-in-law will use a white mother. Please set up a period of time (wine and food. Mother said: "Two Years of farewell, a thousand miles to close the words, what is the sincerity of the letter ?" The saying goes: "giant Qingxin will not default ." Mother said: "If it is natural, it should be beer ." To its day, the giant fruit to the promotion Hall (boarding the hall) worship, have a good time and do not.

Translation: Jin Zhang, Shan Yang (jinzhang, Jinshan County, Shandong province. When I was a young student, I studied in the school too. I was a friend of the same window as Jack Zhang. the two men left the school and returned home at the same time. The paradigm told Zhang that two years later, I will visit your parents to see your children. So we made an appointment. When the date of the appointment was approaching, Zhang told his mother about the matter and asked his mother to prepare the catering and reception paradigm. My mother asked: Have you ever believed in him for two years? Zhang Yi replied: the paradigm is a trusted person, and he will not default. My mother said, if this is the case, I will make the wine for you. On the day of the appointment, the paradigm came. Let's have a good time drinking together. Paradigm and Zhang Yu
The paradigm word is huge, and it is less than that of taixue. Character Generator. They asked for leave to return to their hometown. Expression: "the next two years, when the return, will pass the honorable person ." The communist day. Later, the father-in-law will use a white mother. Please set up a period of time (wine and food. Mother said: "Two Years of farewell, a thousand miles to close the words, what is the sincerity of the letter ?" The saying goes: "giant Qingxin will not default ." Mother said: "If it is natural, it should be beer ." To its day, the giant fruit to the promotion Hall (boarding the hall) worship, have a good time and do not.

Translation: Jin Zhang, Shan Yang (jinzhang, Jinshan County, Shandong province. When I was a young student, I studied in the school too. I was a friend of the same window as Jack Zhang. the two men left the school and returned home at the same time. The paradigm told Zhang that two years later, I will visit your parents to see your children. So we made an appointment. When the date of the appointment was approaching, Zhang told his mother about the matter and asked his mother to prepare the catering and reception paradigm. My mother asked: Have you ever believed in him for two years? Zhang Yi replied: the paradigm is a trusted person, and he will not default. My mother said, if this is the case, I will make the wine for you. On the day of the appointment, the paradigm came. Let's have a good time drinking together. [Original] Fan's word giant Qing ④, shaoyou taixue ⑤, for zhusheng 6, and runan Zhang Yi for friends 7, character uncle. Both of them are in the same village. Expression: "the next two years, when the return, will worship the dear friends, see the son of the Emperor ." The communist day. Later, the old master will be a white mother. Please set up a waiting period. Mother said: "Two years later, let alone a thousand miles to close your speech. Why do you believe in the evil spirits ?" The saying goes: "The Great Qing letter, will not violate the rules ." Mother said: "If it is natural, it should be Erhu liquor ." To its day, the huge fruit to, the Church worship, have a good time and do not.

[Note] ① wenhou: Wei wenhou, Wei Guojun during the Warring States period. Min Ren: Guan Shanze's official. ② Wu Qi: Wei guozuo (now North Cao County, Shandong Province) from the Warring States Period, famous military strategist. ③ Three armies: collectively referred to as the military. ④ Paradigm: Jinxiang people in the Eastern Han Dynasty have successively held positions in Jingzhou, Lujiang taishou, and other posts, with talented and famous talents. ⑤ Taiming: the highest school in Beijing in the Han Dynasty. 6. zhusheng: Many students studying at school. 7. runan: in Henan province today. ⑧: Refers to Zhang's parents. A child refers to the child of Zhang Yi.

[Translation] the paradigm is a huge expression. When I was a young student, I became a student in the school and made friends with Zhang Nan. The word "Yuan" in the zhangshu table. The two will go home at the same time. "Two years later, I will visit your parents and visit your children ." Therefore, they agreed on the date of the meeting, and later agreed on the date, the Yuan Bo begged his mother to prepare a good banquet. Mother Zhang said: after two years of agreement, do you believe this friend will come? Zhang Yan firmly said: the paradigm is a very honest person, and it will never be lost. Two years later, the paradigm came to visit Zhang Ke as scheduled. After dinner, the two were happy to say goodbye. Jin Zhang, Shan Yang (jinzhang, Jinshan County, Shandong province. When I was a young student, I studied in the school too. I was a friend of the same window as Jack Zhang. the two men left the school and returned home at the same time. The paradigm told Zhang that two years later, I will visit your parents to see your children. So we made an appointment. When the date of the appointment was approaching, Zhang told his mother about the matter and asked his mother to wait... for the rest of the text>

[Discrete mathematics] How is the Analytical Paradigm transformed from the generative paradigm?

Deformation:
Q & A (P? 0000p) lead (┐ Q? P)
Q when 1 then (then Q when P)
Q branch (1_q branch P)
(Q? 0000q) lead (Q? P)
1 Gbit/s (Q? P)
Q? P
Q? P is a combination paradigm.
In fact, I think you should have taken this step too. What you don't understand is, "isn't it clearly a form of analysis? How do you say that he is a consortium paradigm ?"
Yes, he does extract the paradigm, but at the same time, he also shares the paradigm, and he is still the master Union paradigm.
It is only in this master Union paradigm that there is only one major item: Q? P.
The definition of a consortium paradigm: a consortium consisting of only a finite simple analytics is called a consortium paradigm.
Q ∨ P fully satisfies the definition. Here, the simple extraction formula is 1.
In addition, the question in your title is "How to transform the disjunction paradigm and the Union paradigm". In fact, there is a gap between the analysis paradigm and the Union paradigm, there is no law that can be directly converted between the primary analytic paradigm and the primary analytic paradigm. You can only perform manual deformation on your own. As a matter of fact, any proposition formula has countless analysis and combination paradigms. Therefore, it is impossible to have a conversion method like the primary analytic paradigm and the primary Union paradigm.
Reference: discrete mathematics