Ordinary multi-valued dependence example
Let the relation model R(U), U = {A, B, C}, let X = {A}, Y = {B}, Z = {C} and Z = U-X- Y. If for any relation r of R(U), given a pair of (A's value, C's value), there is a set of B's value, and this set of B's value only depends on the value of A and has nothing to do with the value of C. When Z is an empty set (that is, there are only two attribute sets of A and B in the relation pattern), it forms an ordinary multi-valued dependence X→→Y. For example, if there is a relationship that represents the student's course selection, assume that the student can only choose one course.(The situation is simplified here for example), the relationship model has an attribute set {student name, course name, teacher name}. If we only consider the two attribute sets {student name} and {course name}, for each student name, the course name is determined (there is no multi-valued situation, because the setting can only choose one course). At this time, if the other attribute sets are regarded as empty sets (here is the attribute set of teacher name), this can be regarded as an ordinary multi-valued dependence. The Extraordinary Ordinary Life novel is equally exciting. Everyone is welcome to click and read it!
Ordinary, multi-valued dependence and non-ordinary
In a multi-valued dependence, let R(U) be a relation pattern on the property set U, X, Y, and Z be a set of U, and Z = U-X- Y. If X→→Y and Z is an empty set, then X→→Y is called a trivial multi-valued dependence; if Z is not empty, then X→→Y is called a non-trivial multi-valued dependence. For example, in the relationship model <Warehouse Manager, Warehouse No., Warehouse Item No.>(Assuming that a product can only be placed in one warehouse, but a warehouse can have several managers), there is a warehouse number corresponding to a <Warehouse Manager, Warehouse Item No.>, but in fact, this warehouse number is only related to the inventory item number and has nothing to do with the manager. This is a manifestation of multi-value dependence. The Extraordinary Ordinary Life novel is equally exciting. Everyone is welcome to click and read it!
Is there only ordinary multi-valued dependence in the 4GN?
4.<strong></strong> Let me explain it to you in detail. ###Fourth Normal Form (4GN) and Multi-valued Dependence (MVR) In database design, 4HF was a very important model. It required that every non-main attribute in the relationship model could not depend on the non-main attributes of other non-main attributes. In other words, a relationship model should have no multi-valued dependence and no joint dependence. Multi-valued dependence refers to the fact that an attribute in a relationship model depends on multiple values of other non-main attribute sets in the relationship model. ###Ordinary and Non-Ordinary Multivalue Dependences - ** Ordinary multi-valued dependence **: When the set of values of Y is a sub-set of X, that is, Y X, the multi-valued dependence X→→Y is called ordinary. This meant that the value of Y was completely determined by the value of X, regardless of whether there were other attributes in Y. - ** Non-trivial multi-valued dependence **: If Y is not a set of X, that is, Y X, then the multi-valued dependence X→→Y is called non-trivial. In this case, the value of Y not only depended on the value of X, but it might also depend on attributes other than X. ### 4 Multivalue Dependences in HF In 4HF, only trivial multi-valued dependence is allowed. This meant that if there were any non-trivial multi-valued dependence, it would need to be eliminated through the database normalisation process. This usually involves breaking down the relationship model into smaller, more manageable parts to ensure data integrity and integrity. Through the above analysis, we can see that there is a close relationship between 4HF and multi-valued dependence, but there are also obvious differences. I hope this information will help you better understand the concepts of 4HF and multi-valued dependence and their application in database design. The Extraordinary Ordinary Life novel is equally exciting. Everyone is welcome to click and read it!
What is the extraordinary multi-valued dependence?
In the relation pattern R(U)(U is the property set), let X, Y, and Z be a set of U, and Z = U-X- Y. If the multi-valued dependence in the relation pattern is true, and the set is not empty, then the multi-valued dependence is called non-trivial. The Extraordinary Ordinary Life novel is equally exciting. Everyone is welcome to click and read it!
Ordinary Dependence and Extraordinary Dependence
Ordinary dependence refers to the dependence of a certain attribute set on itself in the relationship. For example, in a set composed of attributes A and B, the dependence of A and B on themselves (A→A and B→B) is trivial dependence. In a table that stores student performance information, the set of attributes {SNo, CNo, Score},{SNo} → SNo,{CNo, Score} → Score, etc. are also trivial dependence. Nontrivial dependence is if X → Y holds and Y does not belong to X. For example, in a student's report card,{SNo, CNo} → Score is a non-trivial dependence because Score does not belong to the combination key {SNo, CNo}. The Extraordinary Ordinary Life novel is equally exciting. Everyone is welcome to click and read it!
Is ordinary dependence the same as extraordinary dependence?
Ordinary dependence was different from extraordinary dependence. A trivial dependence refers to a property or property set that is completely dependent on itself. For example, in the relationship R(A, B), A -> A and B -> B are trivial dependence. The non-ordinary dependence was not the dependence of this attribute collection on oneself. In the process of database normalisation, trivial dependence had no practical effect and would not affect the integrity or integrity of the database design. It was more used to define and identify more complex dependence relationships, such as functional dependence, partial dependence, and transitive dependence. Non-trivial dependence had different effects and meanings in the design of the database. The Extraordinary Ordinary Life novel is equally exciting. Everyone is welcome to click and read it!
The difference between ordinary dependence and extraordinary dependence
Ordinary Dependence referred to the fact that a certain attribute in the attribute set depended on itself and did not need to obtain information from other attributes. For example, in a table containing the property set {SNo, CNo, Score},{SNo} → SNo, {CNo, Score} → Score is a trivial dependence. A non-trivial dependence is a non-trivial dependence if X → Y is true and Y does not belong to X. For example, in the student report,{SNo, CNo} → Score is a non-trivial dependence, because the score Score does not belong to the combination key {SNo, CNo}. In summary, the main difference between the two was that ordinary dependence was the dependence of attributes on themselves, while non-ordinary dependence was the dependence of an attribute (set) on another attribute (set) that did not belong to itself. The Extraordinary Ordinary Life novel is equally exciting. Everyone is welcome to click and read it!
An example of functional dependence
The following are some examples of functional dependence: 1. In student relationships, the student number determined the student's name, age, and department. It could be expressed as student number → (name, age, department). Since one student number corresponded to one student, once the student number was determined, the corresponding name, age, and faculty would also be determined. 2. In the course selection relationship, the student number and the course number could be added together to determine the results of a student's course, that is,(student number, course number)→ results. A single student number or course number could not determine the results. This was a complete functional dependence. 3. In describing the relationship between students, student number → name, student number → department. Because one student number corresponded to one and only one student, and one student studied in a certain department, when the value of the "student number" attribute was determined, the value of "name" and "department" was also uniquely determined. 4. In the relationship mode, the course number determines the course name, which can be expressed as: course number → course name. The Extraordinary Ordinary Life novel is equally exciting. Everyone is welcome to click and read it!
Which of the following is ordinary dependence?
In the database, ordinary dependence referred to the fact that a certain attribute in the attribute set depended on itself and did not need to obtain information from other attributes. For example, in a set of attributes A and B, the dependence of A and B on themselves (A -> A and B -> B) is a trivial dependence. In a table that stores student performance information (containing the attribute set {SNo, CNo, Score}),{SNo} → SNo,{CNo, Score} → Score, etc. are also trivial dependence. In contrast, if X → Y holds and Y does not belong to X, it is called a non-trivial dependence. For example, in a student's report card,{SNo, CNo} → Score is a non-trivial dependence because the Score does not belong to the combination key {SNo, CNo}. The Extraordinary Ordinary Life novel is equally exciting. Everyone is welcome to click and read it!
An extraordinary example of the ordinary
He recommended a few good novels. Card Creator Traversing the Heavens. The author was a nine-star Card Creator, and the universe was infinite. The male protagonist, Lin Hao, was 19 years old and a Virgo. All kinds of martial arts and divine artifacts could be sealed into the card. It was very cool. " The Rise of the Wind Family in the Waves of Wooden Leaves " was a light novel written by Steamed Dumpling Knight. It told the story of the guardian of Baby Watergate, Wind Wave, who was born and revived his family. " When Reincarnation Invasion " was a novel created by Flower Luo. Reincarnation invaded reality. The protagonist, Abin, felt that the secret realm was the content of movies, anime, and games from his previous life. He was very confident that he was the strongest. The author had many completed books, and there was a shortage of books to read. " Starting from Super God: It's All My Chat Group ", a light novel by Pen and Knife, with the female protagonist, Holy Kesha. " Wilderness: It's Too Difficult to Be a Crown Prince in the Heavenly Court " was a fairy tale and cultivation novel written with pen and paper. There were many interesting stories about Zhang Yang, a transmigrator, being a Crown Prince in the Heavenly Court. The Extraordinary Ordinary Life novel is equally exciting. Everyone is welcome to click and read it!
An example of greatness in the ordinary
" Card Creators Traversing the Heavens " was recommended. The infinite novel written by a nine-star Card Creator was super cool. The male protagonist, Lin Hao, was 19 years old. He could seal anything into a card, such as the Eighteen Dragon Subduing Palms, the Golden Cudgel, and so on. He could even store it on Earth. " I Was a Celestial Being in Journey to the West " was not bad either. It was a Xianxia novel written by an eagle without tentacles. In the world of Journey to the West, Xu Sui was beaten up by the demonic monkey and the Blessed One wanted to pull him into Buddhism. The story was very interesting. " The Infinite Reincarnation of the Denf " was a light novel by the monarch of Heylan. The male protagonist, Huang Chuan, was originally a doctor. He had received the inheritance of the Denf God's Wonder. He was a toxic healer in the world of reincarnation. The plot had elements of revenge and nurturing. Survival in the Cold Current: Lottery from the Little Cabin, a science fiction apocalyptic novel by Tomato Monster. Su Yang relied on the lottery to survive in the dangerous foggy world. " Comic Series: A Dimensional Journey Starting from Lillian ", a comic series novel written by Riyuetian A. The male protagonist had traveled through different dimensions for the Divinity Fragment, and there were many cute female protagonists. The Extraordinary Ordinary Life novel is equally exciting. Everyone is welcome to click and read it!