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  • Database storage for high sample rate data in web app

    - by Jim
    I've got multiple sensors feeding data to my web app. Each channel is 5 samples per second and the data gets uploaded bundled together in 1 minute json messages (containing 300 samples). The data will be graphed using flot at multiple zoom levels from 1 day to 1 minute. I'm using Amazon SimpleDB and I'm currently storing the data in the 1 minute chunks that I receive it in. This works well for high zoom levels, but for full days there will be simply be too many rows to retrieve. The idea I've currently got is that every hour I can crawl through the data and collect together 300 samples for the last hour and store them in an hour Domain (table if you like). Does this sound like a reasonable solution? How have others implemented the same sort of systems?

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  • how to design a schema where the columns of a table are not fixed

    - by hIpPy
    I am trying to design a schema where the columns of a table are not fixed. Ex: I have an Employee table where the columns of the table are not fixed and vary (attributes of Employee are not fixed and vary). Nullable columns in the Employee table itself i.e. no normalization Instead of adding nullable columns, separate those columns out in their individual tables ex: if Address is a column to be added then create table Address[EmployeeId, AddressValue]. Create tables ExtensionColumnName [EmployeeId, ColumnName] and ExtensionColumnValue [EmployeeId, ColumnValue]. ExtensionColumnName would have ColumnName as "Address" and ExtensionColumnValue would have ColumnValue as address value. Employee table EmployeeId Name ExtensionColumnName table ColumnNameId EmployeeId ColumnName ExtensionColumnValue table EmployeeId ColumnNameId ColumnValue There is a drawback is the first two ways as the schema changes with every new attribute. Note that adding a new attribute is frequent. I am not sure if this is the good or bad design. If someone had a similar decision to make, please give an insight on things like foreign keys / data integrity, indexing, performance, reporting etc.

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  • DataSet v/s Database

    - by Hemanshu Bhojak
    While designing applications it is a very good practice to have all the business logic in one place. So why then we sometimes have the business logic in stored procs? Can we fetch all data from the DB and store it in a DataSet and then process it? What would be the performance of the app in this scenario?

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  • Recreation of DB using "mysql mydb < mydb.sql" is really slow when the table has tens of millions of

    - by Jian Lin
    It seems that a MySQL database that has a table with tens of millions of records will get a big INSERT INTO statement when the following mysqldump some_db > some_db.sql is done to back up the database. (is it 1 insert statement that handles all the records?) So when reconstructing the DB using mysql some_db < some_db.sql then the CPU is hardly busy (about 1.8% usage by the mysql process... I don't see a mysqld either?) and also the hard disk doesn't seem to be too busy... Last time, the whole restore process took 5 hours. Is there a way to make it faster? Such as, when doing mysqldump, can it break the INSERT statement into shorter ones, so that the mysql doesn't need to parse the line so hard when restoring the DB?

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  • Database design: Using hundred of fields for little values

    - by user964260
    I'm planning to develop a PHP Web App, it will mainly be used by registered users(sessions) While thinking about the DB design, I was contemplating that in order to give the best user experience possible there would be lots of options for the user to activate, deactivate, specify, etc. For example: - Options for each layout elements, dialog boxes, dashboard, grid, etc. - color, size, stay visible, invisible, don't ask again, show everytime, advanced mode, simple mode, etc. This would get like 100s of fields ranging from simple Yes/No or 1 to N values..., for each user. So, is it having a field for each of these options the way to go? or how do those CRMs or CMS or other Web Apps do it to store lots of 1-2 char long values? Do they group them on Text fields separated by a special char and then "explode" them as an array for runtime usage? thank you

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  • Database strucure for versioning and multiple languages

    - by phobia
    Hi, I'm wondering how to best solve the issue of content existing in multiple versions and multiple languages. An image of my current structure can be seen here: http://i46.tinypic.com/72fx3k.png Each content can only have one active version in each language, and that's how I'm curious on how to best solve. Right now I have a column of the contentversions table, which means for each change of active version I have to run a update and set active=false on all version and then a update to set active=true for the piece of content in question. Any thoughts? :)

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  • ASP.Net 4.0 Database Created Pages

    - by Tyler
    I want to create asp.net 4.0 dynamic pages loaded from my MS SQL server. Basically, its a list of locations with informations. For example: Location1 would have the page www.site.com/location/location1.aspx Location44 would have the page www.site.com/location/location44.aspx I dont even know where to start with this, url writting maybe?

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  • Ruby on Rails and database associations

    - by Marco
    Hi to all, I'm new to the Ruby world, and there is something unclear to me in defining associations between models. The question is: where is the association saved? For example, if i create a Customer model by executing: generate model Customer name:string age:integer and then i create an Order model generate model Order description:text quantity:integer and then i set the association in the following way: class Customer < ActiveRecord::Base has_many :orders end class Order < ActiveRecord::Base belongs_to :customer end I think here is missing something, for example the foreign key between the two entities. How does it handle the associations created with the keywords "has_many" and "belongs_to" ? Thanks

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  • PHP - Select from database the same query

    - by How to PHP
    I created a table that contains the name of the user and his job, and created PHP page that shows me all the users that works doctor, I entered doctor into a variable then I selected from the table where Jobs equal to $doctor, that is great, but I need it to get the same Jobs into a table in the page and the other same jobs into a table in the same page. this is my code that shows only the users works doctor in one table, <html> <h1>Doctors</h1> </html> <?php mysql_connect('localhost','root',''); mysql_select_db('data'); $doctor='doctor'; $query= mysql_query("SELECT * FROM `users` WHERE `job` = '$doctor'")or die(mysql_error()); while ($arr = mysql_fetch_array($query)) $name= $arr['name']; echo $name; } ?> That shows me doctors when I put doctor in a variable I want to show all same Jobs in a table. Is there is a way to do this? Thanks :)

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  • Database Table design for Weekdays and Values

    - by Ved
    Guys, I would love to here your ideas on this. I am creating a table which will store weekly shift hours for employees. for example: Jon works 9:00am tp 9:00pm Monday , 10:00 AM to 5:00PM on Tuseday etc.... How should i go on designing this table. I thought of 2 options. (1) For every record I can have two lines for AM and PM and have columns for Monday to Sunday ID | ParentID | Type | Monday | Tuseday ......Sunday 1 | 1 | AM | 9:00 | 9:00 12:00 2 | 1 | PM | 9:00 | 5:00 02:00 3 | 2 | AM | 10:00 | 4 | 2 | PM | 10:00 | (2) I can save Preference in XML format in one column ID | Info 1 | |Hours|Monday|9:00 AM - 9:00PM|Monday|Tuseday........|Hours Any better ideas ? Thanks

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  • Trying to catch integrity error with sqlaclhemey

    - by Lostsoul
    I'm having problems with trying to catch a error. I'm using pyramid/sqlalchemy and made a sign up form with email as the primary key. The problem is when a duplicate email is entered it raises a IntegrityError, so I'm trying to catch that error and provide a message but no matter what I do I can't catch it(the error keeps appearing). try: new_user = Users(email, firstname, lastname, password) DBSession.add(new_user) return HTTPFound(location = request.route_url('new')) except IntegrityError: message1 = "Yikes! Your email already exists in our system. Did you forget your password?" I get the same message when I tried except exc.SQLAlchemyError (although I want to catch specific errors and not a blanket catch all). Is there something wrong with my python syntax? or is there something I need to do special in sqlalchemy to catch it?

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  • Host...not allowed error in ODBC connection, while connecting to an online MySQL database

    - by sqlchild
    I have downloaded MySQL ODBC Connector 5.1. Now am trying to setup the DSN. But am getting the error: Connection Failed : [HY000] [MySQL] [ODBC 5.1 Driver]Host '117.x.x.x' is not allowed to connect to this MySQL server My server url is server.myweb.com - this name am entering in the TCP/IP Server and Port =3306. I have also entered the userid and password , which is the one which i enter when i open www.myweb.com/cpanel Is this a version problem? Should the version of MySQL on my server also be 5.1, i.e. the one of the ODBC? Please help.

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  • MySQL Database Design with Internationalization

    - by Some name
    Hello, I'm going to start work on a medium sized application, and i'm planning it's db design. One thing that I'm not sure about is this. I will have many tables which will need internationalization, such as: "membership_options, gender_options, language_options etc" Each of these tables will share common i18n fields, like: "title, alternative_title, short_description, description" In your opinion which is the best way to do it? Have an i18n table with the same fields for each of the tables that will need them? or do something like: Membership table Gender table ---------------- -------------- id | created_at id | created_at 1 - 22.03.2001 1 - 14.08.2002 2 - 22.03.2001 2 - 14.08.2002 General translation table ------------------------- record_id | table_name | string_name | alternative_title| .... |id_language 1 - membership regular null 1 (english) 1 - membership normale null 2 (italian) 1 - gender man null 1(english) 1 -gender uomo null 2(italian) This would avoid me repeating something like: membership_translation table ----------------------------- membership_id | name | alternative_title | id_lang 1 regular null 1 1 normale null 2 gender_translation table ----------------------------- gender_id | name | alternative_title | id_lang 1 man null 1 1 uomo null 2 and so on, so i would probably reduce the number of db tables, but i'm not sure about performance.I'm not much of a DB designer, so please let me know.

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  • php database session handling problem in IE8!

    - by psyb0rg
    I've got an html page from where Im making this call periodically: function logon(id) { $.get("data.php", { action: 'online', userID: id}, function(data){ $("#msg").html(data); }); } What this does is it calls this SQL script in data.php: $sql = "update user_sessions set expires=(expires + 2) where userID = $userID"; mysql_query($sql, $conn) or die(mysql_error()); echo $sql; I can see by the echo that the sql syntax and values are correct, but THE CHANGES TO THE expires FIELD ARE NOT DONE, ONLY IN IE8!! It works fine in other ff, safari, chrome, ie6 and 7. There is nothing browser specific about making this sql call, but the user_sessions table is used to store PHP's sessions. Im only increasing the session expiry time when the call is made. What in IE8's session handling is preventing the session time from changing? Is there any caching or cookie problem that needs to be changed?

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  • many to many and integrity when saving the null

    - by user369759
    I have two classes Software, Tag - they are related by ManyToMany. We CAN NOT create Software without putting the Tag to it. I want to write a test which check that: @Test public void createSoftwareWithNullTags() { List<Tag> tags = null; Software software = new Software("software1", "description1", tags); try { software.save(); fail("tags should not be null"); } catch (Exception ex) { // NEVER COME HERE !!! } } So, this test fails. I guess it is not good test for that case - because it even do not try to SAVE data to SOFTWARE_TAG table. Of course i could do validation manually but i want implement it with hibernate, using some annotation or something. Is it possible? Or how would you do this? My entities: @Entity public class Tag extends Model { public String title; public Tag(String title) { this.title = title; } @ManyToMany( cascade = {CascadeType.ALL}, mappedBy = "tags", targetEntity = Software.class ) public List<Software> softwares; } @Entity public class Software extends Model { public String title; public String description; @ManyToOne(optional = false) public Author author; @ManyToMany(cascade = CascadeType.ALL) @JoinTable( name = "SOFTWARE_TAG", joinColumns = @JoinColumn(name = "Software_id"), inverseJoinColumns = @JoinColumn(name = "Tag_id") ) public List<Tag> tags; public Software(String title, String description, Author author, List<Tag> tags) { this.title = title; this.description = description; this.author = author; this.tags = tags; } }

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  • Database schema for a library

    - by ABach
    Hi all - I'm designing a library management system for a department at my university and I wanted to enlist your eyes on my proposed schema. This post is primarily concerned with how we store multiple copies of each book; something about what I've designed rubs me the wrong way, and I'm hoping you all can point out better ways to tackle things. For dealing with users checking out books, I've devised three tables: book, customer, and book_copy. The relationships between these tables are as follows: Every book has many book_copies (to avoid duplicating the book's information while storing the fact that we have multiple copies of that book). Every user has many book_copies (the other end of the relationship) The tables themselves are designed like this: ------------------------------------------------ book ------------------------------------------------ + id + title + author + isbn + etc. ------------------------------------------------ ------------------------------------------------ customer ------------------------------------------------ + id + first_name + first_name + email + address + city + state + zip + etc. ------------------------------------------------ ------------------------------------------------ book_copy ------------------------------------------------ + id + book_id (FK to book) + customer_id (FK to customer) + checked_out + due_date + etc. ------------------------------------------------ Something about this seems incorrect (or at least inefficient to me) - the perfectionist in me feels like I'm not normalizing this data correctly. What say ye? Is there a better, more effective way to design this schema? Thanks!

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  • design an extendable database model

    - by wishi_
    Hi! Currently I'm doing a project whose specifications are unclear - well who doesn't. I wonder what's the best development strategy to design a DB, that's going to be extended sooner or later with additional tables and relations. I want to include "changeability". My main concern is that I want to apply design patterns (it's a university project) and I want to separate the constant factors from those, that change by choosing appropriate design patterns - in my case MVC and a set of sub-patterns at model level. When it comes to the DB however, I may have to resdesign my model in my MVC approach, because my domain model at a later stage my require a different set of classes representing the DB tables. I use Hibernate as an abstraction layer between DB and application. Would you start with a very minimal DB, just a few tables and relations? And what if I want an efficient DB, too? I wonder what strategies are applied in the real world. Stakeholder analysis for example isn't a sufficient planing solution when it comes to changing requirements. I think - at a DB level - my design pattern ends. So there's breach whose impact I'd like to minimize with a smart strategy.

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