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• Working with foreign keys - cannot insert

  - by Industrial

  Hi everyone! Doing my first tryouts with foreign keys in a mySQL database and are trying to do a insert, that fails for this reason: Integrity constraint violation: 1452 Cannot add or update a child row: a foreign key constraint fails Does this mean that foreign keys restrict INSERTS as well as DELETES and/or UPDATES on each table that is enforced with foreign keys relations? Thanks! Updated description: Products ---------------------------- id | type ---------------------------- 0 | 0 1 | 3 ProductsToCategories ---------------------------- productid | categoryid ---------------------------- 0 | 0 1 | 1 Product table has following structure CREATE TABLE IF NOT EXISTS `alpha`.`products` ( `id` MEDIUMINT UNSIGNED NOT NULL AUTO_INCREMENT , `type` TINYINT(2) UNSIGNED NOT NULL DEFAULT 0 , PRIMARY KEY (`id`) , CONSTRAINT `prodsku` FOREIGN KEY (`id` ) REFERENCES `alpha`.`productsToSku` (`product` ) ON DELETE CASCADE, ON UPDATE CASCADE) ENGINE = InnoDB;

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• How to deploy a Java Swing application with an embedded JavaDB database?

  - by Jonas

  I have implemented an Java Swing application that uses an embedded JavaDB database. The database need to be stored somewhere and the database tables need to be created at the first run. What is the preferred way to do these procedures? Should I always create the database in the local directory, and first check if the database file exist, and if it doesn't exist let the user create the tables (or at least show a message that the tables will be created). Or should I let the user choose a path? but then I have to save the path somewhere. Should I save the path with Preferences.systemRoot();, and check if that variable is set on startup? If the user choses a path and save it in the Preferences, can I get any problems with user permissions? or should it be safe wherever the user store the database? Or how do I handle this? Any other suggestions for this procedure?

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• How to optimize an SQL query with many thousands of WHERE clauses

  - by bugaboo

  I have a series of queries against a very mega large database, and I have hundreds-of-thousands of ORs in WHERE clauses. What is the best and easiest way to optimize such SQL queries? I found some articles about creating temporary tables and using joins, but I am unsure. I'm new to serious SQL, and have been cutting and pasting results from one into the next. SELECT doc_id, language, author, title FROM doc_text WHERE language='fr' OR language='es' SELECT doc_id, ref_id FROM doc_ref WHERE doc_id=1234567 OR doc_id=1234570 OR doc_id=1234572 OR doc_id=1234596 OR OR OR ... SELECT ref_id, location_id FROM ref_master WHERE ref_id=098765 OR ref_id=987654 OR ref_id=876543 OR OR OR ... SELECT location_id, location_display_name FROM location SELECT doc_id, index_code, FROM doc_index WHERE doc_id=1234567 OR doc_id=1234570 OR doc_id=1234572 OR doc_id=1234596 OR OR OR x100,000 These unoptimized query can take over 24 hours each. Cheers.

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• SQL Server many-to-many design recommendation

  - by Jean-Philippe Brabant

  I have a SQL Server database with two table : Users and Achievements. My users can have multiple achievements so it a many-to-many relation. At school we learned to create an associative table for that sort of relation. That mean creating a table with a UserID and an AchivementID. But if I have 500 users and 50 achievements that could lead to 25 000 row. As an alternative, I could add a binary field to my Users table. For example, if that field contained 10010 that would mean that this user unlocked the first and the fourth achievements. Is their other way ? And which one should I use.

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• choose append to existing backup instead of overwrite

  - by aron

  Hello, I have a database and I made it's first backup 2 days ago. Then yesterday I spent an entire adding new records. This morning I ran a backup, (but I selected append to existing backup set) as pictured below. I just ran a restore and I found that it wiped out all my data from yesterday and it restored it from the backup of 2 days ago. Not the version from this mornings backup. I zipped this backup file to be safe. I changed some data in the DB, Then I ran the back up again, but this time I selected "overwrite all existing backup sets" Now when I restore the db it's seems to restore the data from the backup correctly. I think I learned a lesson here, correctly if I'm wrong My questions is, Did I lose an entire day of work? I still have this morning's backup .bak file safe in a zip. Is there anyway I can restore is with the right data?

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• How to represent a Many-To-Many relationship in XML or other simple file format?

  - by CSharperWithJava

  I have a list management appliaction that stores its data in a many-to-many relationship database. I.E. A note can be in any number of lists, and a list can have any number of notes. I also can export this data to and XML file and import it in another instance of my app for sharing lists between users. However, this is based on a legacy system where the list to note relationship was one-to-many (ideal for XML). Now a note that is in multiple lists is esentially split into two identical rows in the DB and all relation between them is lost. Question: How can I represent this many-to-many relationship in a simple, standard file format? (Preferably XML to maintain backwards compatibility)

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• Best datastructure for this relationship...

  - by Travis

  I have a question about database 'style'. I need a method of storing user accounts. Some users "own" other user accounts (sub-accounts). However not all user accounts are owned, just some. Is it best to represent this using a table structure like so... TABLE accounts ( ID ownerID -> ID name ) ...even though there will be some NULL values in the ownerID column for accounts that do not have an owner. Or would it be stylistically preferable to have two tables, like so. TABLE accounts ( ID name ) TABLE ownedAccounts ( accountID -> accounts(ID) ownerID -> accounts(ID) ) Thanks for the advice.

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• Unique constraint on more than 10 columns

  - by tk

  I have a time-series simulation model which has more than 10 input variables. The number of distinct simulation instances would be more than 1 million, and each simulation instance generates a few output rows every day. To save the simulation result in a relational database, i designed tables like this. Table SimulationModel { simul_id : integer (primary key), input0 : string or numeric, input1 : string or numeric, ...} Table SimulationOutput { dt : DateTime (primary key), simul_id : integer (primary key), output0 : numeric, ...} My question is, is it fine to put an unique constraint on all of the input columns of SimulationModel table? If it is not a good idea, then what kind of other options do i have to make sure each model is unique?

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• Should I Split Tables Relevant to X Module Into Different DB? Mysql

  - by Michael Robinson

  I've inherited a rather large and somewhat messy codebase, and have been tasked with making it faster, less noodly and generally better. Currently we use one big database to hold all data for all aspects of the site. As we need to plan for significant growth in the future, I'm considering splitting tables relevant to specific sections of the site into different databases, so if/when one gets too large for one server I can more easily migrate some user data to different mysql servers while retaining overall integrity. I would still need to use joins on some tables across the new databases. Is this a normal thing to do? Would I incur a performance hit because of this?

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• How should I build a simple database package for my python application?

  - by Carson Myers

  I'm building a database library for my application using sqlite3 as the base. I want to structure it like so: db/ __init__.py users.py blah.py etc.py So I would do this in Python: import db db.users.create('username', 'password') I'm suffering analysis paralysis (oh no!) about how to handle the database connection. I don't really want to use classes in these modules, it doesn't really seem appropriate to be able to create a bunch of "users" objects that can all manipulate the same database in the same ways -- so inheriting a connection is a no-go. Should I have one global connection to the database that all the modules use, and then put this in each module: #users.py from db_stuff import connection Or should I create a new connection for each module and keep that alive? Or should I create a new connection for every transaction? How are these database connections supposed to be used? The same goes for cursor objects: Do I create a new cursor for each transaction? Create just one for each database connection?

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• Options for storing large text blobs in/with an SQL database?

  - by kdt

  Hi, I have some large volumes of text (log files) which may be very large (up to gigabytes). They are associated with entities which I'm storing in a database, and I'm trying to figure out whether I should store them within the SQL database, or in external files. It seems like in-database storage may be limited to 4GB for LONGTEXT fields in MySQL, and presumably other DBs have similar limits. Also, storing in the database presumably precludes any kind of seeking when viewing this data -- I'd have to load the full length of the data to render any part of it, right? So it seems like I'm leaning towards storing this data out-of-DB: are my misgivings about storing large blobs in the database valid, and if I'm going to store them out of the database then are there any frameworks/libraries to help with that? (I'm working in python but am interested in technologies in other languages too)

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• SQL Server: Log file grows more and more, and do not get merged with the MDF file

  - by SDReyes

  My database files look very suspicious. we are using the DB in a production stage. and I'm seeing how the LDF file grows more and more. while the MDF file seems as it is not growing at all (I don't have a file size history to demonstrate it, but I think it is not doing it!! I bet!) So I guess what could be happening? How could I force the merge to the MDF?

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• Need a field / flag / status number for mutliple use ?

  - by Jules

  I want to create a field in my database which will be easy to query. I think if I give a bit of background this will make more sense. My table has listings shown on my website. I run a program which looks at the listings a decides whether to hide them from being shown on the site. I also hide listings manually for various reasons. I want to store these reasons in a field, so more than one reason could be made for hiding. So I need some form of logic to determine which reasons have been used. Can anyone offer me any guidance on what will be future-proof aka new reasons and what will be quick and easy to query upon ?

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• how to design a db like Facebook where users can update their status and of the fb page as admin

  - by Harsha M V

  i am designing a database where users can update status messages of theirs and they can create pages groups like facebook fan page and post status like the admin of the page and not as a user. user(id, name..) group(id, name...) group_admin(group_id, user_id) this is my set up. Is this the way to do it. How to post under the group as an admin. will i need to make a check to every user if he is the admin or not ?

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• Three customer addresses in one table or in separate tables?

  - by DR

  In my application I have a Customer class and an Address class. The Customer class has three instances of the Address class: customerAddress, deliveryAddress, invoiceAddress. Whats the best way to reflect this structure in a database? The straightforward way would be a customer table and a separate address table. A more denormalized way would be just a customer table with columns for every address (Example for "street": customer_street, delivery_street, invoice_street) What are your experiences with that? Are there any advantages and disadvantages of these approaches?

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• Test Driven Development (TDD) in Visual Studio 2010- Microsoft Mondays

  - by Hosam Kamel

  November 14th , I will be presenting at Microsoft Mondays a session about Test Driven Development (TDD) in Visual Studio 2010 . Microsoft Mondays is program consisting of a series of Webcasts showcasing various Microsoft products and technologies. Each Monday we discuss a particular topic pertaining to development, infrastructure, Office tools, ERP, client/server operating systems etc. The webcast will be broadcast via Lync and can viewed from a web client. The idea behind the “Microsoft Mondays” program is to help you become more proficient in the products and technologies that you use and help you utilize their full potential.   Test Driven Development in Visual Studio 2010 Level – 300 (  Intermediate – Advanced ) Test Driven Development (TDD), also frequently referred to as Test Driven Design, is a development methodology where developers create software by first writing a unit test, then writing the actual system code to make the unit test pass.  The unit test can be viewed as a small specification around how the system should behave; writing it first helps the developer to focus on only writing enough code to make the test pass, thereby helping ensure a tight, lightweight system which is specifically focused meeting on the documented requirements. TDD follows a cadence of “Red, Green, Refactor.” Red refers to the visual display of a failing test – the test you write first will not pass because you have not yet written any code for it. Green refers to the step of writing just enough code in your system to make your unit test pass – your test runner’s UI will now show that test passing with a green icon. Refactor refers to the step of refactoring your code so it is tighter, cleaner, and more flexible. This cycle is repeated constantly throughout a TDD developer’s workday. Date:   November 14, 2011 Time:  10:00 a.m. – 11:00 a.m. (GMT+3)  http://www.eventbrite.com/event/2437620990/efbnen?ebtv=F   See you there! Hosam Kamel Originally posted at

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• New TFS Template Available - "Agile Dev in a Waterfall Environment"–GovDev

  - by Hosam Kamel

    Microsoft Team Foundation Server (TFS) 2010 is the collaboration platform at the core of Microsoft’s application lifecycle management solution. In addition to core features like source control, build automation and work-item tracking, TFS enables teams to align projects with industry processes such as Agile, Scrum and CMMi via the use of customable XML Process Templates. Since 2005, TFS has been a welcomed addition to the Microsoft developer tool line-up by Government Agencies of all sizes and missions. However, many government development teams consistently struggle with leveraging an iterative development process all while providing the structure, visibility and status reporting that is required by many Government, waterfall-centric, project methodologies. GovDev is an open source, TFS Process Template that combines the formality of CMMi/Waterfall with the flexibility of Agile/Iterative: The GovDev for TFS Accelerator also implements two new custom reports to support the customized process and provide the real-time visibility across the lifecycle with full traceability and drill down to tasks, tests and code: The TFS Accelerator contains: A custom TFS process template that implements a requirements centric, yet iterative process with extreme traceability throughout the lifecycle. A custom “Requirements Traceability Report” that provides a single view of traceability for the project.   Within the Traceability Report, you can also view live status indicators and “click-through” to the individual assets (even changesets). A custom report that focuses on “Contributions by Team Member” tracking things like “number of check-ins” and “Net lines added”.  Fully integrated documentation on the entire process and features. For a 45min demo of GovDev, visit: https://msevents.microsoft.com/CUI/EventDetail.aspx?EventID=1032508359&culture=en-us Download it from Codeplex here.     Originally posted at "Hosam Kamel| Developer & Platform Evangelist" http://blogs.msdn.com/hkamel

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• How the "migrations" approach makes database continuous integration possible

  - by David Atkinson

  Testing a database upgrade script as part of a continuous integration process will only work if there is an easy way to automate the generation of the upgrade scripts. There are two common approaches to managing upgrade scripts. The first is to maintain a set of scripts as-you-go-along. Many SQL developers I've encountered will store these in a folder prefixed numerically to ensure they are ordered as they are intended to be run. Occasionally there is an accompanying document or a batch file that ensures that the scripts are run in the defined order. Writing these scripts during the course of development requires discipline. It's all too easy to load up the table designer and to make a change directly to the development database, rather than to save off the ALTER statement that is required when the same change is made to production. This discipline can add considerable overhead to the development process. However, come the end of the project, everything is ready for final testing and deployment. The second development paradigm is to not do the above. Changes are made to the development database without considering the incremental update scripts required to effect the changes. At the end of the project, the SQL developer or DBA, is tasked to work out what changes have been made, and to hand-craft the upgrade scripts retrospectively. The end of the project is the wrong time to be doing this, as the pressure is mounting to ship the product. And where data deployment is involved, it is prudent not to feel rushed. Schema comparison tools such as SQL Compare have made this latter technique more bearable. These tools work by analyzing the before and after states of a database schema, and calculating the SQL required to transition the database. Problem solved? Not entirely. Schema comparison tools are huge time savers, but they have their limitations. There are certain changes that can be made to a database that can't be determined purely from observing the static schema states. If a column is split, how do we determine the algorithm required to copy the data into the new columns? If a NOT NULL column is added without a default, how do we populate the new field for existing records in the target? If we rename a table, how do we know we've done a rename, as we could equally have dropped a table and created a new one? All the above are examples of situations where developer intent is required to supplement the script generation engine. SQL Source Control 3 and SQL Compare 10 introduced a new feature, migration scripts, allowing developers to add custom scripts to replace the default script generation behavior. These scripts are committed to source control alongside the schema changes, and are associated with one or more changesets. Before this capability was introduced, any schema change that required additional developer intent would break any attempt at auto-generation of the upgrade script, rendering deployment testing as part of continuous integration useless. SQL Compare will now generate upgrade scripts not only using its diffing engine, but also using the knowledge supplied by developers in the guise of migration scripts. In future posts I will describe the necessary command line syntax to leverage this feature as part of an automated build process such as continuous integration.

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• Click No Browse: How to Navigate Objects Without Opening Them

  - by thatjeffsmith

  Oracle SQL Developer by default automatically opens the object editor when you click on an object in your connection tree or schema browser. For most folks this is very convenient. But if you are selecting objects to drag them to a model or to the worksheet, this can get annoying as the focus of the screen changes when you don’t want it to. The other scenario this feature might disrupt more than delight is when you want to click around the database in the tree and every time you click on an object, the object editor automatically changes to the selected object. You can disable this automatic browsing behavior in SQL Developer by modifying this preference: Tools Preferences Database ObjectViewer Open Object on Single Click Disable this if you don’t want an object to open when you click on it OK, I do realize my description of the problem may have confused the heck out of you just now. So instead of more words, how about a couple of animations of the object-click behavior with the option ON and OFF? Preference Disabled Click, no open. Double click, open. Preference Enabled (Default) As you click on objects, they are automatically opened

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• Including BLOB images in your PDF Reports

  - by thatjeffsmith

  Earlier this year we walked through how to work with BLOBs in Oracle SQL Developer. So you already know how to INSERT, UPDATE and view the BLOBs stored in your tables. But now I want to show you how to include those images in your PDF reports. You know how to work with SQL Developer reports, right? No? OK, let’s do a quick run down memory lane then: How to Build a Bar Chart Child reports – click on parent record for on-the-fly children records Alright, so if you have a GRID report that contains a BLOB column, you have the option of including the BLOB contents when you create a PDF export: At design time, specify how you want the BLOB content to be treated when you export to PDF Note that you must specify the treatment of the BLOBs in the report design. You won’t be prompted when you launch the Export wizard dialog. When you open your PDF, there will be a link to the image. Click it. Click then confirm. It will launch the default image viewer on your machine. I hope your pictures are more excited than mine.

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• Use Those Schemas, People!

  - by BuckWoody

  Database Schemas are just containers – they aren’t users or anything else – think of a sub-directory on the hard drive. In early versions of SQL Server we “hid” schemas, placing all objects under “dbo”, which gave the erroneous perception that Schemas are users. In SQL Server 2005, we “un-hid” or re-introduced schemas within the database. Users can have a default schema (a place where their new objects go), you can add new schemas and transfer objects between them, and they have many other benefits. But I still see a lot of applications, developed by shops I know as well as vendors, that don’t make use of a Schema. Everything is piled under dbo. I completely understand this – since permissions can be granted to a schema, they feel a lot like a user, so it’s just easier not to worry about both users and schemas when you create a database. But if you’ll use them properly you can make your application more understandable and portable. You should at least take a few minutes and read more about them – you owe it to your users: http://msdn.microsoft.com/en-us/library/ms190387.aspx Share this post: email it! | bookmark it! | digg it! | reddit! | kick it! | live it!

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• Best pattern for storing (product) attributes in SQL Server

  - by EdH

  We are starting a new project where we need to store product and many product attributes in a database. The technology stack is MS SQL 2008 and Entity Framework 4.0 / LINQ for data access. The products (and Products Table) are pretty straightforward (a SKU, manufacturer, price, etc..). However there are also many attributes to store with each product (think industrial widgets). These may range from color to certification(s) to pipe size. Every product may have different attributes, and some may have multiples of the same attribute (Ex: Certifications). The current proposal is that we will basically have a name/value pair table with a FK back to the product ID in each row. An example of the attributes Table may look like this: ProdID AttributeName AttributeValue 123 Color Blue 123 FittingSize 1.25 123 Certification AS1111 123 Certification EE2212 123 Certification FM.3 456 Pipe 11 678 Color Red 999 Certification AE1111 ... Note: Attribute name would likely come from a lookup table or enum. So the main question here is: Is this the best pattern for doing something like this? How will the performance be? Queries will be based on a JOIN of the product and attributes table, and generally need many WHEREs to filter on specific attributes - the most common search will be to find a product based on a set of known/desired attributes. If anyone has any suggestions or a better pattern for this type of data, please let me know. Thanks! -Ed

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• Struggling with a data modeling problem

  - by rpat

  I am struggling with a data model (I use MySQL for the database). I am uneasy about what I have come up with. If someone could suggest a better approach, or point me to some reference matter I would appreciate it. The data would have organizations of many types. I am trying to do a 3 level classification (Class, Category, Type). Say if I have 'Italian Restaurant', it will have the following classification Food Services Restaurants Italian However, an organization may belong to multiple groups. A restaurant may also serve Chinese and Italian. So it will fit into 2 classifications Food Services Restaurants Italian Food Services Restaurants Chinese The classification reference tables would be like the following: ORG_CLASS (RowId, ClassCode, ClassName) 1, FOOD, Food Services ORG_CATEGORY(RowId, ClassCode, CategoryCode, CategoryName) 1, FOOD, REST, Restaurants ORG_TYPE (RowId, ClassCode, CategoryCode, TypeCode, TypeName) 100, FOOD, REST, ITAL, Italian 101, FOOD, REST, CHIN, Chinese 102, FOOD, REST, SPAN, Spanish 103, FOOD, REST, MEXI, Mexican 104, FOOD, REST, FREN, French 105, FOOD, REST, MIDL, Middle Eastern The actual data tables would be like the following: I will allow an organization a max of 3 classifications. I will have 3 GroupIds each pointing to a row in ORG_TYPE. So I have my ORGANIZATION_TABLE ORGANIZATION_TABLE (OrgGroupId1, OrgGroupId2, OrgGroupId3, OrgName, OrgAddres) 100,103,NULL,MyRestaurant1, MyAddr1 100,102,NULL,MyRestaurant2, MyAddr2 100,104,105, MyRestaurant3, MyAddr3 During data add, a dialog could let the user choose the clssa, category, type and the corresponding GroupId could be populated with the rowid from the ORG_TYPE table. During Search, If all three classification are chosen, It will be more specific. For example, if Food Services Restaurants Italian is the criteria, the where clause would be 'where OrgGroupId1 = 100' If only 2 levels are chosen Food Services Restaurants I have to do 'where OrgGroupId1 in (100,101,102,103,104,105, .....)' - There could be a hundred in that list I will disallow class level search. That is I will force selection of a class and category The Ids would be integers. I am trying to see performance issues and other issues. Overall, would this work? or I need to throw this out and start from scratch.

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• Graph-structured databases and Php

  - by stagas

  I want to use a graph database using php. Can you point out some resources on where to get started? Is there any example code / tutorial out there? Or are there any other methods of storing data that relate to each other in totally random/abstract situations? - Very abstract example of the relations needed: John relates to Mary, both relate to School, John is Tall, Mary is Short, John has Blue Eyes, Mary has Green Eyes, query I want is which people are related to 'Short people that have Green Eyes and go to School' - answer John - Another example: TrackA -> ArtistA -> ArtistB -> AlbumA -----> [ label ] -> AlbumB -----> [ A ] -> TrackA:Remix -> Genre:House -> [ Album ] -----> [ label ] TrackB -> [ C ] [ B ] Example queries: Which Genre is TrackB closer to? answer: House - because it's related to Album C, which is related to TrackA and is related to Genre:House Get all Genre:House related albums of Label A : result: AlbumA, AlbumB - because they both have TrackA which is related to Genre:House - It is possible in MySQL but it would require a fixed set of attributes/columns for each item and a complex non-flexible query, instead I need every attribute to be an item by itself and instead of 'belonging' to something, to be 'related' to something.

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• Building a News-feed that comprises posts "created by user's connections" && "on the topics user is following"

  - by aklin81

  I am working on a project of Questions & Answers website that allows a user to follow questions on certain topics from his network. A user's news-feed wall comprises of only those questions that have been posted by his connections and tagged on the topics that he is following(his expertise topics). I am confused what database's datamodel would be most fitting for such an application. The project needs to consider the future provisions for scalability and high performance issues. I have been looking at Cassandra and MySQL solutions as of now. After my study of Cassandra I realized that Simple news-feed design that shows all the posts from network would be easy to design using Cassandra by executing fast writes to all followers of a user about the post from user. But for my kind of application where there is an additional filter of 'followed topics', (ie, the user receives posts "created by his network" && "on topics user is following"), I could not convince myself with a good schema design in Cassandra. I hope if I missed something because of my short understanding of cassandra, perhaps, can you please help me out with your suggestions of how this news-feed could be implemented in Cassandra ? Looking for a great project with Cassandra ! Edit: There are going to be maximum 5 tags allowed for tagging the question (ie, max 5 topics can be tagged on a question).

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