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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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• Creating a test database with copied data *and* its own data

  - by Jordan Reiter

  I'd like to create a test database that each day is refreshed with data from the production database. BUT, I'd like to be able to create records in the test database and retain them rather than having them be overwritten. I'm wondering if there is a simple straightforward way to do this. Both databases run on the same server, so apparently that rules out replication? For clarification, here is what I would like to happen: Test database is created with production data I create some test records that I want to keep running on the test server (basically so I can have example records that I can play with) Next day, the database is completely refreshed, but the records I created that day are retained. Records that were untouched that day are replaced with records from the production database. The complication is if a record in the production database is deleted, I want it to be deleted on the test database too, so I do want to get rid of records in the test database that no longer exist in the production database, unless those records were created within the test database. Seems like the only way to do this would be to have some sort of table storing metadata about the records being created? So for example, something like this: CREATE TABLE MetaDataRecords ( id integer not null primary key auto_increment, tablename varchar(100), action char(1), pk varchar(100) ); DELETE FROM testdb.users WHERE NOT EXISTS (SELECT * from proddb.users WHERE proddb.users.id=testdb.users.id) AND NOT EXISTS (SELECT * from testdb.MetaDataRecords WHERE testdb.MetaDataRecords.pk=testdb.users.pk AND testdb.MetaDataRecords.action='C' AND testdb.MetaDataRecords.tablename='users' );

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• Designing application flow

  - by Umesh Awasthi

  I am creating a web application in java where I need to mock the following flow. When user trigger a certain process (add product to cart), I need to pass through following steps Need to see in HTTP Session if user is logged in. Check HTTP Session if shopping cart is there If user exist in HTTP Session and his/her cart do not exist in HTTP Session Get user cart from the database. add item to cart and save it to HTTP session and update cart in DB. If cart does not exist in DB, create new cart and and save in it HTTP Session. Though I missed a lot of use cases here (do not want question length to increase a lot), but most of the flow will be same as I described in above steps. My flow will start from the Controller and will go towards Service Layer and than ends up in the DAO layer. Since there will be a lot of use cases where I need to check HTTP session and based on that need to call Service layer, I was planning to add a Facade layer which should be responsible to do this for me like checking Session and interacting with Service layer. Please suggest if this is a valid approach or any other best approach can be implemented here? One more point where I am confused is how to handle HTTP session in facade layer? do I need to pass HTTP session object each time I call my Facade or any other approach can be used here?

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• Where ORMs blur the lines between code and data, how do you decide what logic should be a stored procedure, and what should be coded?

  - by PhonicUK

  Take the following pseudocode: CreateInvoiceAndCalculate(ItemsAndQuantities, DispatchAddress, User); And say CreateInvoice does the following: Create a new entry in an Invoices table belonging to the specified User to be sent to the given DispatchAddress. Create a new entry in an InvoiceItems table for each of the items in ItemsAndQuantities, storing the Item, the Quantity, and the cost of the item as of now (by looking it up from an Items table) Calculate the total amount of the invoice (ex shipping and taxes) and store it in the new Invoice row. At a glace you wouldn't be able to tell if this was a method in my applications code, or a stored procedure in the database that is being exposed as a function by the ORM. And to some extent it doesn't really matter. Now technically none of this is business logic. You're not making any decisions - just performing a calculation and creating records. However some may argue that because you are performing a calculation that affects the business (the total amount to be invoiced) that this isn't something that should be done in a stored procedure and instead should be in code. So for this specific example - why would it be more appropriate to do one or the other? And where do you draw the line? Or does it even particular matter as long as it's sufficiently well documented?

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• How to model an address type in DDD?

  - by Songo

  I have an User entity that has a Set of Address where Address is a value object: class User{ ... private Set<Address> addresses; ... public setAddresses(Set<Address> addresses){ //set all addresses as a batch } ... } A User can have a home address and a work address, so I should have something that acts as a look up in the database: tbl_address_type ------------------------------------------------ | address_type_id | address_type | ------------------------------------------------ | 1 | work | ------------------------------------------------ | 2 | home | ------------------------------------------------ and correspondingly tbl_address ------------------------------------------------------------------------------------- | address_id | address_description |address_type_id| user_id | ------------------------------------------------------------------------------------- | 1 | 123 main street | 1 | 100 | ------------------------------------------------------------------------------------- | 2 | 456 another street | 1 | 100 | ------------------------------------------------------------------------------------- | 3 | 789 long street | 2 | 200 | ------------------------------------------------------------------------------------- | 4 | 023 short street | 2 | 200 | ------------------------------------------------------------------------------------- Should the address type be modeled as an Entity or Value type? and Why? Is it OK for the Address Value object to hold a reference to the Entity AdressType (in case it was modeled as an entity)? Is this something feasible using Hibernate/NHibernate? If a user can change his home address, should I expose a User.updateHomeAddress(Address homeAddress) function on the User entity itself? How can I enforce that the client passes a Home address and not a work address in this case? (a sample implementation is most welcomed) If I want to get the User's home address via User.getHomeAddress() function, must I load the whole addresses array then loop it and check each for its type till I found the correct type then return it? Is there a more efficient way than this?

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• What's the "best" database for embedded?

  - by mawg

  I'm an embedded guy, not a database guy. I've been asked to redesign an existing system which has bottlenecks in several places. The embedded device is based around an ARM 9 processor running at 220mHz. There should be a database of 50k entries (may increase to 250k) each with 1k of data (max 8 filed). That's approximate - I can try to get more precise figures if necessary. They are currently using SqlLite 2 and planning to move to SqlLite 3. Without starting a flame war - I am a complete d/b newbie just seeking advice - is that the "best" decision? I realize that this might be a "how long is a piece of string?" question, but any pointers woudl be greatly welcomed. I don't mind doing a lot of reading & research, but just hoped that you could get me off to a flying start. Thanks. p.s Again, a total rewrite, might not even stick with embedded Linux, but switch to eCos, don't worry too much about one time conversion between d/b formats. Oh, and accesses should be infrequent, at most one every few seconds. edit: ok, it seems they have 30k entries (may reach 100k or more) of only 5 or 6 fields each, but at least 3 of them can be a search key for a record. They are toying with "having no d/b at all, since the data are so simple", but it seems to me that with multiple keys, we couldn't use fancy stuff like a quicksort() type search (recursive, binary search). Any thoughts on "no d/b", just data-structures? Btw, one key is 800k - not sure how well SqlLite handles that (maybe with "no d/b" I have to hash that 800k to something smaller?)

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• How often are design patterns used in the workplace using PHP

  - by Metropolis

  Hey everyone, I read a book awhile back called PHP Design Patterns and Practice, and ever since then I have been using design patterns whenever I think they are needed. However it just occurred to me that maybe most companies do not use design patterns very often for PHP, or at all. What I was wondering is, do most companies use design patterns to help improve code flexibility? And if so, what are the best design patterns to learn for PHP? Thanks for any help on this, Metropolis

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• how many index per database table?

  - by sam

  Hi, How many indexes is preferred for one table in MYSQL?? I have a company table where I search mostly for ID,state and category? Thansk

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• how to generate dbml file from Sybase database?

  - by 5YrsLaterDBA

  I think we may have trouble with our existing project. For some reasons we have to switch from SQL Server to Sybase SQL Anywhere 11. now we trying to find a way continue use our existing LINQ code. We wish we can still use L2S? If cannot, we wish we can use L2E, then we have to change to ADO. how to generate dbml file from Sybase Anywhere 11? after that can we use sqlmetal to generate .cs files?

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• how to design a database for a specific website.

  - by Steven Spielberg

  i want to design a Database for a website. how i can design it better. are you know any particular thing, tips , technique to design it in better way. in a table of information user can allow to website to show it or hide it. how can i do this like info1 = show info2 = show info3 = show i have a much more field that user can be showed and hide. how i can handle this situation or condition in Database

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• Need help to create database schema for wholesale online tee store

  - by techiepark

  Hi, I'm currently working on wholesale online t-shirt shop. I have done this for fixed quantity and price, and its working fine. Now i need to do this for variable quantity and price. Here is the reference link, like what i have to do. Basic tables i have created are - CREATE TABLE attribute ( attribute_id int(11) NOT NULL auto_increment, name varchar(100) NOT NULL, PRIMARY KEY (attribute_id) ); CREATE TABLE attribute_value ( attribute_value_id int(11) NOT NULL auto_increment, attribute_id int(11) NOT NULL, value varchar(100) NOT NULL, PRIMARY KEY (attribute_value_id), KEY idx_attribute_value_attribute_id (attribute_id) ); CREATE TABLE product ( product_id int(11) NOT NULL auto_increment, name varchar(100) NOT NULL, description varchar(1000) NOT NULL, price decimal(10,2) NOT NULL, image varchar(150) default NULL, thumbnail varchar(150) default NULL, PRIMARY KEY (product_id), FULLTEXT KEY idx_ft_product_name_description (name,description) ); CREATE TABLE product_attribute ( product_id int(11) NOT NULL, attribute_value_id int(11) NOT NULL, PRIMARY KEY (product_id,attribute_value_id) ); I'm not getting how to store the price based on variable quantity. Please help me to create product and its related tables. my requirement is same as above reference link.

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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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• 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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• 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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• 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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• 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 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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• 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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