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• Buddy List: Relational Database Table Design

  - by huntaub

  So, the modern concept of the buddy list: Let's say we have a table called Person. Now, that Person needs to have many buddies (of which each buddy is also in the person class). The most obvious way to construct a relationship would be through a join table. i.e. buddyID person1_id person2_id 0 1 2 1 3 6 But, when a user wants to see their buddy list, the program would have to check the column 'person1_id' and 'person2_id' to find all of their buddies. Is this the appropriate way to implement this kind of table, or would it be better to add the record twice.. i.e. buddyID person1_id person2_id 0 1 2 1 2 1 So that only one column has to be searched. Thanks in advance.

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• Database solutions for storing/searching EXIF data

  - by webdestroya

  I have thousands of photos on my site (each with a numeric PhotoID) and I have EXIF data (photos can have different EXIF tags as well). I want to be able to store the data effectively and search it. Some photos have more EXIF data than others, some have the same, so on.. Basically, I want to be able to query say 'Select all photos that have a GPS location' or 'All photos with a specific camera' I can't use MySQL (tried it, it doesn't work). I thought about Cassandra, but I don't think it lets me query on fields. I looked at SimpleDB, but I would rather: not pay for the system, and I want to be able to run more advanced queries on the data. Also, I use PHP and Linux, so it would be awesome if it could interface nicely to PHP. Any ideas?

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• Best way to auto-restore db on an houlry basis

  - by aron

  Hello, I have a demo site where anyone can login and test a management interface. Every hour I would like to flush all the data in the SQL 2008 Database and restore it from the original. Rae Gate sql has some awesome tools for this, however they are beyond my budget right now. Could I simply make a backup copy of the database's data file, then have a c# console app that deletes it and copies over the original. Then I can have a windows schedule task to run the .exe every hour. It's simple and free... would this work? I'm using SQL Server 2008 R2 Web edition I understand that red gate is technically better because I can set it to analyze the db and only update the records that were altered, and the approach I have above is like a "sledge hammer".

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• How do I normalise this database design?

  - by Ian Roke

  I am creating a rowing reporting and statistics system for a client where I have a structure at the moment similar to the following: ----------------------------------------------------------------------------- | ID | Team | Coaches | Rowers | Event | Position | Time | ----------------------------------------------------------------------------- | 18 | TeamName | CoachName1 | RowerName1 | EventName | 1 | 01:32:34 | | | | CoachName2 | RowerName2 | | | | | | | | RowerName3 | | | | | | | | RowerName4 | | | | ----------------------------------------------------------------------------- This is an example row of data but I would like to expand this out to a Rowers table and Coaches table and so on but I don't know how best to then link that back to the Entries table which is what this is. Has anybody got any words of wisdom they could share with me? Update A Team can have any number of Coaches and Rowers, a Rower can be in many Teams (Team A, B, C etc) and a Team can have many Coaches.

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• Database that consumes less disk space

  - by Hugo Palma

  I'm looking at solutions to store a massive quantity of information consuming the less possible disk space. The information structure is very simple and the queries will also be very simple. I've looked at solutions like Apache Cassandra and relations databases but couldn't find a comparison where disk usage is mentioned. Any ideas on this would be great.

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• Rating System Database Structure

  - by Harsha M V

  I have two entity groups. Restaurants and Users. Restaurants can be rated (1-5) by users. And rating fromeach user should be retrievable. Resturant(id, name, ..... , total_number_of_votes, total_voting_points ) User (id, name ...... ) Rating (id, restaurant_id, user_id, rating_value) Do i need to store the avg value so that it need not be calculated every time ? which table is the best place to store avg_rating, total_no_of_votes, total_voting_points ?

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• Database model for saving random boolean expressions

  - by zarko.susnjar

  I have expressions like this: (cat OR cats OR kitten OR kitty) AND (dog OR dogs) NOT (pigeon OR firefly) Anyone having idea how to make tables to save those? Before I got request for usage of brackets, I limited usage of operators to avoid ambiguous situations. So only ANDs and NOTs or only ORs and saved those in this manner: operators id | name 1 | AND 2 | OR 3 | NOT keywords id | keyword 1 | cat 2 | dog 3 | firefly expressions id | operator | keywordId 1 | 0 | 1 1 | 1 | 2 1 | 3 | 3 which was: cat AND dog NOT firefly But now, I'm really puzzled...

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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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• Why dont people simply use "Object Database"s ?

  - by umanga

  Instead of JDO , Hibernate , iBATIS why we can not simply use "Object DataBases" ? http://en.wikipedia.org/wiki/Comparison_of_object_database_management_systems

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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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• Why is it bad to use boolean flags in databases? And what should be used instead?

  - by David Chanin

  I've been reading through some of guides on database optimization and best practices and a lot of them suggest not using boolean flags at all in the DB schema (ex http://forge.mysql.com/wiki/Top10SQLPerformanceTips). However, they never provide any reason as to why this is bad. Is it a peformance issue? is it hard to index or query properly? Furthermore, if boolean flags are bad, what should you use to store boolean values in a database? Is it better to store boolean flags as an integer and use a bitmask? This seems like it would be less readable.

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• Database: Storing Dates as Numeric Values

  - by Chin

  I'm considering storing some date values as ints. i.e 201003150900 Excepting the fact that I lose any timezone information, is there anything else I should be concerned about with his solution? Any queries using this column would be simple 'where after or before' type lookups. i.e Where datefield is less than 201103000000 (before March next year). currently the app is using MSSQL2005. Any pointers to pitfalls appreciated.

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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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• 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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• 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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• 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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• 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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• 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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• 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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• Pros and Cons for CreatedDate and ModifiedDate columns in all database tables

  - by Ismail

  What are the pros and cons? When should we have them and when we shouldn't?

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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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• With modern social networking and scaling, can Cassandra replace the standard relational database su

  - by alex

  Is it possible to build the entire social networking application on cassandra? Sure, it takes longer to set up, but it scales much better. Correct? Please list the situations when Cassandra should be used.

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• What tools do you use to plan and draw a database structure = tables, relationship

  - by EugeneP

  Modeling tool or just a visual tool for drawing. In fact I only need to draw and later I'll transform the picture into sql by hand to better control the process.

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• What music players (or related applications) are there that would allow displaying/editing embedded lyrics of music tracks?

  - by cipricus

  I use OSD Lyrics and CoverGloobus. They are good, they search and eventually download lyrics, when they can find them. The sources used by OSD Lyrics, for example, are rather limited (although I love the way it displays them. The latter accesses a reacher database, but the display is not adjustable as far as I know). Couldn't find a way to make these programs see lyrics from a file selected by me. What I want is to be able to add the lyrics myself, and even to embed them into the music file - and, of course, to display them from there. The last feature alone would be very valuable to me, as I have a large music database with lyrics already embedded, but I cannot see them with these programs: they are just looking for new lyrics on the Internet, although the lyrics are on my computer. In Windows I used Foobar2000 to find, display and embed lyrics (with the add-on lyricsgrabber) and when I needed to add the lyrics manually I used to embed them in MediaMonkey (this player allows finding them, but also editing and embedding - just by copy/paste). I am not able to run MediaMonkey in Wine. Foobar works, but with a lot of problems. And anyway, Wine is of last resort. I am looking for a Linux program that would be able to do something similar to what I have described above.

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