normalizing | 易学教程

Dealing with “hypernormalized” data

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问题 My employer, a small office supply company, is switching suppliers and I am looking through their electronic content to come up with a robust database schema; our previous schema was pretty much just thrown together without any thought at all, and it's pretty much led to an unbearable data model with corrupt, inconsistent information. The new supplier's data is much better than the old one's, but their data is what I would call hypernormalized . For example, their product category structure

What's the better database design: more tables or more columns? [closed]

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问题 Closed . This question is opinion-based. It is not currently accepting answers. Want to improve this question? Update the question so it can be answered with facts and citations by editing this post. Closed 3 years ago . A former coworker insisted that a database with more tables with fewer columns each is better then one with fewer tables with more columns each. For example rather than a customer table with name, address, city, state, zip, etc. columns, you would have a name table, an

Normalizing an existing MS Access Database

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问题 I have one large access database that I need to normalize into five tables and a lookup table. I understand the theory behind normalization and have already sketched out the look of the tables but I am lost on how to transform my table to get the database normalized. The table analyzers doesn't offer the the breakdown that I want. 回答1: If you have a single table, add an Autonumber field to it. Then create your other tables, and use the Autonumber value from the original single table as the

Address book DB schema

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问题 I need to store contact information for users. I want to present this data on the page as an hCard and downloadable as a vCard. I'd also like to be able to search the database by phone number, email, etc. What do you think is the best way to store this data? Since users could have multiple addresses, etc complete normalization would be a mess. I'm thinking about using XML, but I'm not familiar with querying XML db fields. Would I still be able to search for users by contact info? I'm using

Address book DB schema

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I need to store contact information for users. I want to present this data on the page as an hCard and downloadable as a vCard . I'd also like to be able to search the database by phone number, email, etc. What do you think is the best way to store this data? Since users could have multiple addresses, etc complete normalization would be a mess. I'm thinking about using XML, but I'm not familiar with querying XML db fields. Would I still be able to search for users by contact info? I'm using SQL Server 2005, if that matters. Consider two tables for People and their addresses: People (pid,

Hierarchical tagging in SQL

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问题 I have a PHP web application which uses a MySQL database for object tagging, in which I've used the tag structure accepted as the answer to this SO question. I'd like to implement a tag hierarchy, where each tag can have a unique parent tag. Searches for a parent tag T would then match all descendants of T (i.e. T, tags whos parent is T (children of T), grandchildren of T, etc.). The easiest way of doing this seems to be to add a ParentID field to the tag table, which contains the ID of a tag

What is the need for normalizing a vector?

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Trying to understand vectors a bit more. What is the need for normalizing a vector? If I have a vector, N = (x, y, z) What do you actually get when you normalize it - I get the idea you have to divide x/|N| y/|N| & z/|N|. My question is, why do we do this thing, I mean what do we get out of this equation? What is the meaning or 'inside' purpose of doing this. A bit of a maths question, I apologize, but I am really not clear in this topic. That's a bit like asking why we multiply numbers. It comes up all the time. The Cartesian coordinate system that we use is an orthonormal basis (consists of

Data structure for non-overlapping ranges within a single dimension

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问题 I need a data structure that can store non-overlapping ranges within a single dimension. The entire range of the dimension need not be completely covered. An example would be a conference room scheduler. The dimension is time. No two schedules may overlap. The conference room isn't always scheduled. In other words, for a given time there can be at most one schedule. A quick solution is for a range to store the start and end times. Range { Date start Date end } This is non-normalized and

What is the need for normalizing a vector?

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问题 Trying to understand vectors a bit more. What is the need for normalizing a vector? If I have a vector, N = (x, y, z) What do you actually get when you normalize it - I get the idea you have to divide x/|N| y/|N| & z/|N|. My question is, why do we do this thing, I mean what do we get out of this equation? What is the meaning or 'inside' purpose of doing this. A bit of a maths question, I apologize, but I am really not clear in this topic. 回答1: That's a bit like asking why we multiply numbers.

How do you determine how far to normalize a database?

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When creating a database structure, what are good guidelines to follow or good ways to determine how far a database should be normalized? Should you create an un-normalized database and split it apart as the project progresses? Should you create it fully normalized and combine tables as needed for performance? sergeb You want to start designing a normalized database up to 3rd normal form. As you develop the business logic layer you may decide you have to denormalize a bit but never, never go below the 3rd form. Always, keep 1rd and 2nd form compliant. You want to denormalize for simplicity of