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  • Using Entity Framework, how do I specify a sort on a navagation property?

    - by Jared
    I have two tables: [Category], [Item]. They are connected by a join table: [CategoryAndItem]. It has two primary key fields: [CategoryKey], [ItemKey]. Foreign keys exist appropriately and Entity has no problem pulling this in and creating the correct navigation properties that connect the entity objects. Basically each category can have multiple items, and items can be in multiple categories. The problem is that the order of items is specified per category, so that a particular item might be third in one category but fifth in another. In the past, I have added a [Sequence] field to the join table and modified the stored procedure to handle it. But since Entity is replacing my stored procedures, I need to figure out how to make Entity handle the sequence. Any suggestions?

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  • Web Shop Schema - Document Db

    - by Maxem
    I'd like to evaluate a document db, probably mongo db in an ASP.Net MVC web shop. A little reasoning at the beginning: There are about 2 million products. The product model would be pretty bad for rdbms as there'd be many different kinds of products with unique attributes. For example, there'd be books which have isbn, authors, title, pages etc as well as dvds with play time, directors, artists etc and quite a few more types. In the end, I'd have about 9 different products with a combined column count (counting common columns like title only once) of about 70 to 100 whereas each individual product has 15 columns at most. The three commonly used ways in RDBMS would be: EAV model which would have pretty bad performance characteristics and would make it either impractical or perform even worse if I'd like to display the author of a book in a list of different products (think start page, recommended products etc.). Ignore the column count and put it all in the product table: Although I deal with somewhat bigger databases (row wise), I don't have any experience with tables with more than 20 columns as far as performance is concered but I guess 100 columns would have some implications. Create a table for each product type: I personally don't like this approach as it complicates everything else. C# Driver / Classes: I'd like to use the NoRM driver and so far I think i'll try to create a product dto that contains all properties (grouped within detail classes like book details, except for those properties that should be displayed on list views etc.). In the app I'll use BookBehavior / DvdBehaviour which are wrappers around a product dto but only expose the revelent Properties. My questions now: Are my performance concerns with the many columns approach valid? Did I overlook something and there is a much better way to do it in an RDBMS? Is MongoDb on Windows stable enough? Does my approach with different behaviour wrappers make sense?

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  • Using memory-based cache together with conventional cache

    - by Industrial
    Hi! Here's the deal. We would have taken the complete static html road to solve performance issues, but since the site will be partially dynamic, this won't work out for us. What we have thought of instead is using memcache + eAccelerator to speed up PHP and take care of caching for the most used data. Here's our two approaches that we have thought of right now: Using memcache on all<< major queries and leaving it alone to do what it does best. Usinc memcache for most commonly retrieved data, and combining with a standard harddrive-stored cache for further usage. The major advantage of only using memcache is of course the performance, but as users increases, the memory usage gets heavy. Combining the two sounds like a more natural approach to us, even though the theoretical compromize in performance. Memcached appears to have some replication features available as well, which may come handy when it's time to increase the nodes. What approach should we use? - Is it stupid to compromize and combine the two methods? Should we insted be focusing on utilizing memcache and instead focusing on upgrading the memory as the load increases with the number of users? Thanks a lot!

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  • BI with Django?

    - by Helmut
    Is there a way to develop Bi (Business Intelligence) solutions with Django? Therefore it should be possible to define models with more than one Datasource. Is anybody out there who has experienced BI with Django? How could it work ?

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  • Tool Compare the tables in two different databeses

    - by user191124
    I am using Toad. Frequently i need to compare tables in two different test environments. the tables present in them are same but the data differs. i just need to know what are the differences in the same tables which are in two different data bases.Are there any tools which can be installed on windows and use it to compare. Much appreciate your help:)

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  • MySQL - query to return CSV in a field?

    - by StackOverflowNewbie
    Assume I have the following tables: TABLE: foo - foo_id (PK) TABLE: tag - tag_id (PK) - name TABLE: foo_tag - foo_tag_id (PK) - foo_id (FK) - tag_id (FK) How do I query this so that I get a result like this: ========================== | foo_id | tags | ========================== | 1 | foo, bar | | 2 | foo | | 3 | bar | -------------------------- Basically, I need all of foo's tags in one column, comma separated. Possible in MySQL?

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  • Is it possible to partition more than one way at a time in SQL Server?

    - by meeting_overload
    I'm considering various ways to partition my data in SQL Server. One approach I'm looking at is to partition a particular huge table into 8 partitions, then within each of these partitions to partition on a different partition column. Is this even possible in SQL Server, or am I limited to definining one parition column+function+scheme per table? I'm interested in the more general answer, but this strategy is one I'm considering for Distributed Partitioned View, where I'd partition the data under the first scheme using DPV to distribute the huge amount of data over 8 machines, and then on each machine partition that portion of the full table on another parition key in order to be able to drop (for example) sub-paritions as required.

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  • How to achieve high availability?

    - by tanyehzheng
    My boss wants to have a system that takes into concern of continent wide catastrophic event. He wants to have two servers in US and two servers in Asia (1 login server and 1 worker server in each continent). In the event that earthquake breaks the connection between the two continents, both should work alone. When the connection is revived, they should sync each other back to normal. External cloud system not allowed as he has no confidence. The system should take into account of scalability which means addition of new servers should be easy to configure. The servers should be load balanced. The connection between the servers should be very secure(encrypted and send through SSL although SSL takes care of encryption). The system should let one and only one user log in with one account. (beware of latency between continent and two users sharing account may reach both login server at the same time) Please help. I'm already at the end of my wit. Thank you in advance.

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  • Version of SQLite used in Android?

    - by Eno
    Reason: Im wondering how to handle schema migrations. The newer SQLite versions support an "ALTER TABLE" SQL command which would save me having to copy data, drop the table, recreate table and re-insert data.

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  • What's wrong with this SQL query?

    - by ThinkingInBits
    I have two tables: photographs, and photograph_tags. Photograph_tags contains a column called photograph_id (id in photographs). You can have many tags for one photograph. I have a photograph row related to three tags: boy, stream, and water. However, running the following query returns 0 rows SELECT p.* FROM photographs p, photograph_tags c WHERE c.photograph_id = p.id AND (c.value IN ('dog', 'water', 'stream')) GROUP BY p.id HAVING COUNT( p.id )=3 Is something wrong with this query?

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  • Detecting changes between rows with same ID

    - by Noah
    I have a table containing some names and their associated ID, along with a snapshot: snapshot, id, name I need to identify when a name has changed for an id between snapshots. For example, in the following data: 1, 0, 'MOUSE_SPEED' 1, 1, 'MOUSE_POS' 1, 2, 'KEYBOARD_STATE' 2, 0, 'MOUSE_BUTTONS' 2, 1, 'MOUSE_POS' 2, 2, 'KEYBOARD_STATE' ...the meaning of id 0 changed with snapshot 2, but the others remained the same. I'd like to construct a query that (ideally) returns: 1, 0, 'MOUSE_SPEED' 2, 0, 'MOUSE_BUTTONS' I am using PostgreSQL v8.4.2.

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  • using dummy row with NOT NULL to solve DEFAULT NULL

    - by Tony38
    I know having DEFAULT NULLS is not a good practice but I have many optional lookup values which are FK in the system so to solve this issue here is what i am doing: I use NOT NULL for every FK / lookup colunms. I have the first row in every lookup table which is PK id = 1 as a dummy row with just "none" in all the columns. This way I can use NOT NULL in my schema and if needed reference to the none row values PK =1 for FKs which do not have any lookup value. Is this a good design or any other work arounds? EDIT: I have: Neighborhood table Postal table. Every neighborhood has a city, so the FK can be NOT NULL. But not every postal code belongs to a neighborhood. Some do, some don't depending on the country. So if i use NOT NULL for the FK between postal and neighborhood then I will be screwed as there has to be some value entered. So what i am doing in essence is: have a row in every table to be a dummy row just to link the FKs. This way row one in neighborhood table will be: n_id = 1 name =none etc... In postal table I can have: postal_code = 3456A3 FK (city) = Moscow FK (neighborhood_id)=1 as a NOT NULL. If I don't have a dummy row in the neighborhood lookup table then I have to declare FK (neighborhood_id) as a Default null column and store blanks in the table. This is an example but there is a huge number of values which will have blanks then in many tables.

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  • Are there any examples/tutorials of using Spring 3.0 with Cassandra as a backend?

    - by zeroDivisible
    Hello, As I had written in title, I am trying to learn Spring 3.0 (I already know Django, Pylons and few simpler MVC frameworks) and try to use Cassandra as a backend for my web application. Are there any real world examples of doing this? Or maybe some tutorials? I know about the existence of documentation of both technologies, yet I am looking for something "faster" to read and get me rolling.

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  • Idea for a small project, should I use Python?

    - by Robb
    I have a project idea, but unsure if using Python would be a good idea. Firstly, I'm a C++ and C# developer with some SQL experience. My day job is C++. I have a project idea i'd like to create and was considering developing it in a language I don't know. Python seems to be popular and has piqued my interests. I definitely use OOP in programming and I understand Python would work fine with that style. I could be way off on this, I've only read small bits and pieces about the language. The project won't be public or anything, just purely something of my own creation do dabble in at home. So the project would essentially represent a simple game idea I have. The game would consist roughly these things: Data structures to hold specific information (would be strongly typed). A way to output the gamestate for the players. This is completely up in the air, it can be graphical or text based, I don't really care at this point. A way to save off game data for the players in something like a database or file system. A relatively easy way for me to input information and a 'GO' button which processes the changes and obviously creates a new gamestate. The game would function similar to a board game. Really nothing out of the ordinary when I look back at that list. Would this be a fun way to learn Python or should I select another language?

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  • Does Ruby on Rails "has_many" array provide data on a "need to know" basis?

    - by Jian Lin
    On Ruby on Rails, say, if the Actor model object is Tom Hanks, and the "has_many" fans is 20,000 Fan objects, then actor.fans gives an Array with 20,000 elements. Probably, the elements are not pre-populated with values? Otherwise, getting each Actor object from the DB can be extremely time consuming. So it is on a "need to know" basis? So does it pull data when I access actor.fans[500], and pull data when I access actor.fans[0]? If it jumps from each record to record, then it won't be able to optimize performance by doing sequential read, which can be faster on the hard disk because those records could be in the nearby sector / platter layer -- for example, if the program touches 2 random elements, then it will be faster just to read those 2 records, but what if it touches all elements in random order, then it may be faster just to read all records in a sequential way, and then process the random elements. But how will RoR know whether I am doing only a few random elements or all elements in random?

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  • SQL SERVER - Detecting non-indexed columns but used in WHERE clause

    - by Vadi
    How to detect a column included in WHERE clause but used in indexed? Little Background: Until the time the table has few number of records things will be okay, once it started having millions of records then index should be created for a column which is used in WHERE clauses in stored procs, inline queries etc., Since we have hundreds of stored procs and queries that often gets changed by the devs I wanted to have a automated way of identifying those columns that are used in WHERE clauses but not an index is created. How to do that in SQL SERVER 2008?

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  • Passing BLOB/CLOB as parameter to PL/SQL function

    - by Ula Krukar
    I have this procedure i my package: PROCEDURE pr_export_blob( p_name IN VARCHAR2, p_blob IN BLOB, p_part_size IN NUMBER); I would like for parameter p_blob to be either BLOB or CLOB. When I call this procedure with BLOB parameter, everything is fine. When I call it with CLOB parameter, I get compilation error: PLS-00306: wrong number or types of arguments in call to 'pr_export_blob' Is there a way to write a procedure, that can take either of those types as parameter? Some kind of a superclass maybe?

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  • How Implement a system to determine if a milestone has been reached

    - by Luc M
    I have a table named stats player_id team_id match_date goal assist` 1 8 2010-01-01 1 1 1 8 2010-01-01 2 0 1 9 2010-01-01 0 5 ... I would like to know when a player reach a milestone (eg 100 goals, 100 assists, 500 goals...) I would like to know also when a team reach a milestone. I want to know which player or team reach 100 goals first, second, third... I thought to use triggers with tables to accumulate the totals. Table player_accumulator (and team_accumulator) table would be player_id total_goals total_assists 1 3 6 team_id total_goals total_assists 8 3 1 9 0 5 Each time a row is inserted in stats table, a trigger will insert/update player_accumulator and team_accumulator tables. This trigger could also verify if player or team has reached a milestone in milestone table containing numbers milestone 100 500 1000 ... A table player_milestone would contains milestone reached by player: player_id stat milestone date 1 goal 100 2013-04-02 1 assist 100 2012-11-19 There is a better way to implements a "milestone" ? There is an easiest way without triggers ? I'm using PostgreSQL

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