database-normalization

问题 I currently have a table called "RESOURCES" with a keywords field called "RES_Tags". The "RES_Tags" field contains a comma-delimited list of keywords for each record. I need to normalize this table/field. I have already set up the following tables: TAGS, TAGS_TO_RESOURCES. Please see the schema here: http://sqlfiddle.com/#!9/edac4/1 What is a query that will allow me to parse the keywords in RES_Tags, write them into the TAGS table without creating duplicates and then write a listing in the

问题 I am struggling to understand 4NF, 5NF, and their difference. Here is the way I would describe 4/5NF (or, how I would describe the steps to achieve it) to someone who doesn't know. I am stating this because this will show what I have really understood. Typically, a N:N entity relationship should be implemented by having a join table for their possible combinations. If there are 3 or more entities connected with N:N relationships, one should consider carefully: The more general(including)

问题 I am trying to normalize the following table. I want to go from the UNF form to 3NF form. I want to know, what do you do at the 1NF stage? It says it's where you remove the repetitive columns or groups (ex. ManagerID, ManagerName). This is considered repetitive because it's leads to the same data. The Unnormalized data table has the following columns CustomerRental(CustNo,CustName,PropNo,PAddress,RentStart,RentFinish,Rent,OwnerNo,OName) There are no repeating columns/fields and each cell has

问题 The error I'm getting is: ERROR 1366 (HY000): Incorrect DECIMAL value: '0' for column '' at row -1 I'm trying to normalize a database and ensuring that the data types are correct. Inserting data from BASE_TABLE into a new table named Inventors . This is the query I'm using to insert. If I take a single row manually from the select query it can correctly insert into the Inventors table. However, running the query like this I instantly get the error above. INSERT INTO Inventors(ID,Firstname

问题 I want to know which normal form a canonical cover is in. I know before doing normalization we find the canonical cover so I think it is in first normal form. But it may be in no normal form as the definition of 1NF by Wikipedia is no row should have a duplicate: First normal form enforces below criteria: Eliminate repeating groups in individual tables. Create a separate table for each set of related data. Identify each set of related data with a primary key 回答1: Normal forms apply to

问题 i am confused about mvd violation, simply i cant figure out anything that will violate mvd, for example there are A B C three columns, each row is a tuple A B C a2 b2 c1 a1 b1 c2 a1 b1 c3 a2 b3 c1 does B->>C and B->>A? thanks 回答1: An MVD, just like an FD, is a rule . It applies to your business case or not, you'll need to inspect the requirements and/or the specs in order to know. You cannot know whether it applies from looking at sample data (that applies to FD's as well). Looking at sample

问题 I want to count N consecutive days that a specific user has meetings, on a given date and before it. For example: count the consecutive meeting days that a user with id 1 has at 16 January 2013. I found some good answers here and here but the tables are not in normal form like my sample above and i cannot figure out how to implement it for my occasion. A sample table structure as follows: CREATE TABLE IF NOT EXISTS `meetings` ( `id` int(10) unsigned NOT NULL AUTO_INCREMENT, `time` datetime

问题 I'm a jr. developer (5 months on the job), and I have a question about data normalization. Now, as I understand it, the general principle behind data normalization is to create a RDBMS where data redundancy is kept to a minimum. In my project, one of the DB people created a DB. We have 50+ tables, and the tables in the DB are usually very fragmented, ie. a table has two or three columns and that's it. Now, when it comes to writing sql queries, it has become something of a minor hassle since

问题 I'm interested in learning about tools that operate like this: Given a database schema and some data, suggest whether the schema is likely structured in any particular normal form, and then tell how the schema might be factored to produce further normalization. Basically, a static analysis tool for database schema design. Like other static analysis tools, such a database tool need not generate perfect results (I doubt such a "perfect" tool is computationally feasible), or applicable to all

问题 Assignment: Consider a relation 𝑅(𝐴,𝐵,𝐶,𝐷,𝐸,𝐺,𝐻) and its FD set 𝐹 = {𝐴𝐵 → 𝐶𝐷, 𝐸 → 𝐷, 𝐴𝐵𝐶 → 𝐷𝐸, 𝐸 → 𝐴𝐵, 𝐷 → 𝐴𝐺, 𝐴𝐶𝐷 → 𝐵𝐸}. Decompose it into a collection of BCNF relations if it is not in BCNF. Make sure your decomposition is lossless-join. Explanation Hi, I'm working on my database homework (relation design chapter). I think I've commanded the basic process based on in-class examples. However, the tricky part here is we have an attribute 'H' which has no relation with others, which confuses