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  • Need to work out database structure

    - by jim smith
    Hi, Just need a little kickstart with this. I have Mysql/PHP, and I have 5,000 products. I have 30 companies I need to store some data for those 30 companies for each product as follows: a) prices b) stock qty I also need to store data historically on a daily basis. So the table... It makes sense that the records will be the products because there's 5000, and if I put the companies as the columns, I can store the prices, but what about the stock quantities? I could create two columns for each compoany, one for prices, one for qty. Then make the tablename the date for that day...so theer would be a new table for every day with 5000 products in it? is this the correct way? Some idea on how I'll be retreiving data the top 5 lowest prices (and the company) by product for a certain date the price and stock changes in the past 7 days by product

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  • How to map to tables in database PHPMyAdmin

    - by thegrede
    I'm working now on a project which a user can save their own coupon codes on the websites, so I want to know what is the best to do that, Lets say, I have 1 table with the users, like this, userId | firstName | lastName | codeId and then I have a table of the coupon codes, like this, codeId | codeNumber So what I can do is to connect the codeId to userId so when someone saves the coupons goes the codeId from the coupon table into the codeId of the users table, But now what if when a user have multiple coupons what do I do it should be connected to the user? I have 2 options what to do, Option 1, Saving the codeId from coupons table into the codeId of users table like 1,2,3,4,5, Option 2 To make a new row into the coupons table and to connect the user to the code with adding another field in the coupon table userId and putting into it the user which has added the coupon his userId of the users table, So what of the two options is better to do? Thanks you guys.

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  • Database Modelling - Conceptually different entities but with near identical fields

    - by Andrew Shepherd
    Suppose you have two sets of conceptual entities: MarketPriceDataSet which has multiple ForwardPriceEntries PoolPriceForecastDataSet which has multiple PoolPriceForecastEntry Both different child objects have near identical fields: ForwardPriceEntry has MarketPriceDataSetId (foreign key to parent table) StartDate EndDate SimulationItemId ForwardPrice PoolPriceForecastEntry has PoolPriceForecastDataSetId (foreign key to parent table) StartDate EndDate SimulationItemId ForecastPoolPrice If I modelled them as separate tables, the only difference would be the foreign key, and the name of the price field. There has been a debate as to whether the two near identical tables should be merged into one. Options I've thought of to model this is: Just keep them as two independent, separate tables Have both sets in the one table with an additional "type" field, and a parent_id equalling a foreign key to either parent table. This would sacrifice referential integrity checks. Have both sets in the one table with an additional "type" field, and create a complicated sequence of joining tables to maintain referential integrity. What do you think I should do, and why?

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  • correct approach to store in database

    - by John
    I'm developing an online website (using Django and Mysql). I have a Tests table and User table. I have 50 tests within the table and each user completes them at their own pace. How do I store the status of the tests in my DB? One idea that came to my mind is to create an additional column in User table. That column containing testid's separated by comma or any other delimiter. userid | username | testscompleted 1 john 1, 5, 34 2 tom 1, 10, 23, 25 Another idea was to create a seperate table to store userid and testid. So, I'll have only 2 columns but thousands of rows (no of tests * no of users) and they will always continue to increase. userid | testid 1 1 1 5 2 1 1 34 2 10

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  • database is normalized but the following is a problem please help

    - by user287745
    but the prob is there are relations ships which are so huge that after normalizing they have like a 20 primary keys( composite keys) which are really foreign keys but have to be declared as primary keys to identify the relationship uniquely. so please help? is it correct and i apologize to the expert community for not accepting answers, i was not aware that accepting is possible, the TICK MARK is that visible :-)

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  • friendship database schema

    - by Daniel Hertz
    I'm creating a db schema that involves users that can be friends, and I was wondering what the best way to model the ability for these friends to have friendships. Should it be its own table that simply has two columns that each represent a user? Thanks!

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  • Database table relationships: Always also relate to specified value (Linq to SQL in .NET Framework)

    - by sinni800
    I really can not describe my question better in the title. If anyone has suggestions: Please tell! I use the Linq to SQL framework in .NET. I ran into something which could be easily solved if the framework supported this, it would be a lot of extra coding otherwise: I have a n to n relation with a helper table in between. Those tables are: Items, places and the connection table which relates items to places and the other way. One item can be found in many places, so can one place have many items. Now of course there will be many items which will be in ALL places. Now there is a problem: Places can always be added. So I need a place-ID which encompasses ALL places, always. Like maybe a place-id "0". If the helper table has a row with the place-id of zero, this should be visible in all places. In SQL this would be a simple "Where [...] or place-id = 0", but how do I do this in Linq relations? Also, for a little side question: How could I manage "all but this place" kind of exclusions?

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  • Generic version control strategy for select table data within a heavily normalized database

    - by leppie
    Hi Sorry for the long winded title, but the requirement/problem is rather specific. With reference to the following sample (but very simplified) structure (in psuedo SQL), I hope to explain it a bit better. TABLE StructureName { Id GUID PK, Name varchar(50) NOT NULL } TABLE Structure { Id GUID PK, ParentId GUID (FK to Structure), NameId GUID (FK to StructureName) NOT NULL } TABLE Something { Id GUID PK, RootStructureId GUID (FK to Structure) NOT NULL } As one can see, Structure is a simple tree structure (not worried about ordering of children for the problem). StructureName is a simplification of a translation system. Finally 'Something' is simply something referencing the tree's root structure. This is just one of many tables that need to be versioned, but this one serves as a good example for most cases. There is a requirement to version to any changes to the name and/or the tree 'layout' of the Structure table. Previous versions should always be available. There seems to be a few possibilities to tackle this issue, like copying the entire structure, but most approaches causes one to 'loose' referential integrity. Example if one followed this approach, one would have to make a duplicate of the 'Something' record, given that the root structure will be a new record, and have a new ID. Other avenues of possible solutions are looking into how Wiki's handle this or go a lot further and look how proper version control systems work. Currently, I feel a bit clueless how to proceed on this in a generic way. Any ideas will be greatly appreciated. Thanks leppie

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  • Database design - table relationship question

    - by iama
    I am designing schema for a simple quiz application. It has 2 tables - "Question" and "Answer Choices". Question table has 'question ID', 'question text' and 'answer id' columns. "Answer Choices" table has 'question ID', 'answer ID' and 'answer text' columns. With this simple schema it is obvious that a question can have multiple answer choices & hence the need for the answer choices table. However, a question can have only one correct answer and hence the need for the 'answer ID' in the question table. However, this 'answer ID' column in the question table provides a illusion as though there can be multiple questions for a single answer which is not correct. The other alternative to eliminate this illusion is to have another table just for correct answer that will have just 2 columns namely the question ID and the answer ID with a 1-1 relationship between the two tables. However, I think this is redundant. Any recommendation on how best to design this thereby enforcing the rules that a question can have multiple answer choices but only one correct answer? Many Thanks.

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  • Database Modelling - Conceptually different entities with near identical fields

    - by Andrew Shepherd
    Suppose you have two sets of conceptual entities: MarketPriceDataSet which has multiple ForwardPriceEntries PoolPriceForecastDataSet which has multiple PoolPriceForecastEntry Both different child objects have near identical fields: ForwardPriceEntry has StartDate EndDate SimulationItemId ForwardPrice MarketPriceDataSetId (foreign key to parent table) PoolPriceForecastEntry has StartDate EndDate SimulationItemId ForecastPoolPrice PoolPriceForecastDataSetId (foreign key to parent table) If I modelled them as separate tables, the only difference would be the foreign key, and the name of the price field. There has been a debate as to whether the two near identical tables should be merged into one. Options I've thought of to model this is: Just keep them as two independent, separate tables Have both sets in the one table with an additional "type" field, and a parent_id equalling a foreign key to either parent table. This would sacrifice referential integrity checks. Have both sets in the one table with an additional "type" field, and create a complicated sequence of joining tables to maintain referential integrity. What do you think I should do, and why?

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  • Naming of boolean column in database table

    - by Space Cracker
    I have 'Service' table and the following column description as below Is User Verification Required for service ? Is User's Email Activation Required for the service ? Is User's Mobile Activation required for the service ? I Hesitate in naming these columns as below IsVerificationRequired IsEmailActivationRequired IsMobileActivationRequired or RequireVerification RequireEmailActivation RequireMobileActivation I can't determined which way is the best .So, Is one of the above suggested name is the best or is there other better ones ?

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  • Upgrading from SQL2000 database to SQL Express 2008 R2

    - by itwb
    Hi, We have a web application which uses a MSSQL 2000 backend database. We are currently paying a ridiculous amount for Shared Hosting, with the database costs alone costing us $150 per month (MSSQL 100mb extra space is $40 per month). Our database size is 896.38 MB I am looking at getting a Virtual Private Server and upgrading the database to a MSSQL2008 Express database. I am aware that the Express version is limited to a 10GB database (with R2), and is constrained to a single CPU. I have also been offered SQL Server 2008 Web Edition for $19/per month, but I cannot find many details on the difference between Express and Web. Any suggestions here? What I would also like to know is: If we upgrade the database to MSSQL 2008 database, is there any issues with possible data transformations in the future? I.e. Is it possible to download and mount it with SQL Server 2008 Standard edition? I'm more concerned about how to get data in and out of the database through SQL Management tools. Are there any other issues that I might face? Thanks, Mike

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  • MySQL root user can't access database

    - by Ed Schofield
    Hi all, We have a MySQL database ('myhours') on a production database server that is accessible to one user ('edsf') only, but not to the root user. The command 'SHOW DATABASES' as the root user does not list the 'myhours' database. The same command as the 'edsf' user lists the database: mysql> SHOW DATABASES; +--------------------+ | Database | +--------------------+ | information_schema | | myhours | +--------------------+ 2 rows in set (0.01 sec) Only the 'edsf' user can access the 'myhours' database with 'USE myhours'. Neither user seems to have permission to grant further permissions for this database. My questions are: Q1. How is it that the root user does not have permission to use the database? How could this have come about? The output of SHOW GRANTS FOR 'root'@'localhost'; looks fine to me: GRANT ALL PRIVILEGES ON *.* TO 'root'@'localhost' IDENTIFIED BY PASSWORD '*xxx' WITH GRANT OPTION Q2. How can I recover this situation to make this database visible to the MySQL root user and grant further permissions on it? Thanks in advance for any help! -- Ed

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  • Problems locating Redmine database

    - by zordor
    I have an active redmine but I can not find the database where it is running right now. It should be on PostgreSQL but the database where it should be running is empty. Does anybody have any idea how to check current database used by redmine? Please let me know if you need any extra information. Thank you EDIT: Ok I know the database it is using. On the database.yml I have project_redmine but it is using the database project I dont know why. That database it is used by developers for the actual project. So that is getting me problems of course. I am unable to run it on the right DB (project_redmine) any ideas? :S

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  • Separate tables or single table with queries?

    - by Joe
    I'm making an employee information database. I need to handle separated employees. Should I a. set up a query with a macro to send separated employees to a separate table, or b. just add a flag to the single table denoting separation? I understand that it's best practice to take choice b, and the one reason I can think of for this is that any structural changes I make to the table later will have to be done in both places. But it also seems like setting up a flag forces me to filter out that flag for basically every useful query I'm going to make in the future.

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  • Centrally managing 100+ websites without bankrupting a small company

    - by palintropos
    I'm mainly interested in opinions on the trade-offs between having a single central server all the websites connect to as opposed to each website mirroring a subset of the master database with all the products in it. For example, will I run into severe performance issues (or even security issues, or restrictions) making queries to an offsite database? Will we hit scalability issues we can't handle early on from the sheer bandwidth required to maintain this? If we do go with something like a script that keeps smaller databases (each containing a subset of the central master data) in sync, what sorts of issues will we likely encounter there? I would really like the opinions of people far more knowledgeable than I am regarding the pros and cons of both setups and what headaches we are likely to encounter. CLARIFICATION: This should not be viewed as a question about whether we should implement one database vs multiple databases. This question has been answered numerous times. The question is regarding the pros and cons for a deployment like this having the ability to manage all the websites centrally (one server) vs trying to keep them all in sync if they each have their own db (multiple servers). REAL-WORLD EXAMPLE: We are a t-shirt company, and we have individual websites for our different kinds of t-shirts, but we're looking at a central order management integrated with our single shopping cart (which is ColdFusion + MySQL). Now, let's say we have a t-shirt that's on 10 of our websites and we change an image for it. Ideally we would change that in one place and the change would propagate, but how would we set this up?

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  • Using Queries with Coherence Read-Through Caches

    - by jpurdy
    Applications that rely on partial caches of databases, and use read-through to maintain those caches, have some trade-offs if queries are required. Coherence does not support push-down queries, so queries will apply only to data that currently exists in the cache. This is technically consistent with "read committed" semantics, but the potential absence of data may make the results so unintuitive as to be useless for most use cases (depending on how much of the database is held in cache). Alternatively, the application itself may manually "push down" queries to the database, either retrieving results equivalent to querying the cache directly, or may query the database for a key set and read the values from the cache (relying on read-through to handle any missing values). Obviously, if the result set is too large, reading through the cache may cause significant thrashing. It's also worth pointing out that if the cache is asynchronously synchronized with the database (perhaps via database change listener), that an application may commit a transaction to the database, then generate a key set from the database via a query, then read cache entries through the cache, possibly resulting in a race condition where the application sees older data than it had previously committed. In theory this is not problematic but in practice it is very unintuitive. For this reason it often makes sense to invalidate the cache when updating the database, forcing the next read-through to update the cache.

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  • Relational vs. Dimensional Databases, what's the difference?

    - by grautur
    I'm trying to learn about OLAP and data warehousing, and I'm confused about the difference between relational and dimensional modeling. Is dimensional modeling basically relational modeling, but allowing for redundant/un-normalized data? For example, let's say I have historical sales data on (product, city, # sales). I understand that the following would be a relational point-of-view: Product | City | # Sales Apples, San Francisco, 400 Apples, Boston, 700 Apples, Seattle, 600 Oranges, San Francisco, 550 Oranges, Boston, 500 Oranges, Seattle, 600 While the following is a more dimensional point-of-view: Product | San Francisco | Boston | Seattle Apples, 400, 700, 600 Oranges, 550, 500, 600 But it seems like both points of view would nonetheless be implemented in an identical star schema: Fact table: Product ID, Region ID, # Sales Product dimension: Product ID, Product Name City dimension: City ID, City Name And it's not until you start adding some additional details to each dimension that the differences start popping up. For instance, if you wanted to track regions as well, a relational database would tend to have a separate region table, in order to keep everything normalized: City dimension: City ID, City Name, Region ID Region dimension: Region ID, Region Name, Region Manager, # Regional Stores While a dimensional database would allow for denormalization to keep the region data inside the city dimension, in order to make it easier to slice the data: City dimension: City ID, City Name, Region Name, Region Manager, # Regional Stores Is this correct?

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  • Still Confused About Identifying vs. Non-Identifying Relationships

    - by Jason
    So, I've been reading up on identifying vs. non-identifying relationships in my database design, and a number of the answers on SO seem contradicting to me. Here are the two questions I am looking at: What's the Difference Between Identifying and Non-Identifying Relationships Trouble Deciding on Identifying or Non-Identifying Relationship Looking at the top answers from each question, I appear to get two different ideas of what an identifying relationship is. The first question's response says that an identifying relationship "describes a situation in which the existence of a row in the child table depends on a row in the parent table." An example of this that is given is, "An author can write many books (1-to-n relationship), but a book cannot exist without an author." That makes sense to me. However, when I read the response to question two, I get confused as it says, "if a child identifies its parent, it is an identifying relationship." The answer then goes on to give examples such as SSN (is identifying of a Person), but an address is not (because many people can live at an address). To me, this sounds more like a case of the decision between primary key and non-primary key. My own gut feeling (and additional research on other sites) points to the first question and its response being correct. However, I wanted to verify before I continued forward as I don't want to learn something wrong as I am working to understand database design. Thanks in advance.

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  • How do you decide what kind of database to use?

    - by Jason Baker
    I really dislike the name "NoSQL", because it isn't very descriptive. It tells me what the databases aren't where I'm more interested in what the databases are. I really think that this category really encompasses several categories of database. I'm just trying to get a general idea of what job each particular database is the best tool for. A few assumptions I'd like to make (and would ask you to make): Assume that you have the capability to hire any number of brilliant engineers who are equally experienced with every database technology that has ever existed. Assume you have the technical infrastructure to support any given database (including available servers and sysadmins who can support said database). Assume that each database has the best support possible for free. Assume you have 100% buy-in from management. Assume you have an infinite amount of money to throw at the problem. Now, I realize that the above assumptions eliminate a lot of valid considerations that are involved in choosing a database, but my focus is on figuring out what database is best for the job on a purely technical level. So, given the above assumptions, the question is: what jobs are each database (including both SQL and NoSQL) the best tool for and why?

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  • any practices ,samples for ERD?

    - by just_name
    Q: I wanna any web sites , any books just for training on ERD and normalization ,, i wanna a lot of samples ,practices,and case studies with recommended answers, to strength myself in database design.and avoid the poor data base design i made . note:i don't need books to explain the concepts , what i need is practices ,examples,case studies with recommended answers. Thanks in advance.

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