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  • How to design model for multi-tiered data?

    - by Chris
    Say I have three types of object: Area, Subarea and Topic. I want to be able to display an Area, which is just a list of Subareas and the Topics contained in those Subareas. I never want to be able to display Subareas separately - they're just for breaking up the Topics. Topics can, however, appear in multiple Areas (but probably under the same Subarea). How would I design a model for this? I could use ForeignKey from Topic to Subarea and from Subarea to Area, but it seems unnecessarily complex given that I never want to interact with subareas themselves. Also, none of these objects are ever altered or added to by the user. They're just for me to represent information. Maybe there is a better way to represent it all?

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  • what is the out put?

    - by user329820
    Hi this is my code but when I run it in mysql it will show an error because of datatype but my friend checked it with sql server and it doesn't show error and also insert the value: 32769 .which of them is correct? CREATE TABLE T1 (A INTEGER NOT NULL); INSERT T1 VALUES (32768.5);

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  • Most efficient way to maintain a 'set' in SQL Server?

    - by SEVEN YEAR LIBERAL ARTS DEGREE
    I have ~2 million rows or so of data, each row with an artificial PK, and two Id fields (so: PK, ID1, ID2). I have a unique constraint (and index) on ID1+ID2. I get two sorts of updates, both with a distinct ID1 per update. 100-1000 rows of all-new data (ID1 is new) 100-1000 rows of largely, but not necessarily completely overlapping data (ID1 already exists, maybe new ID1+ID2 pairs) What's the most efficient way to maintain this 'set'? Here are the options as I see them: Delete all the rows with ID1, insert all the new rows (yikes) Query all the existing rows from the set of new data ID1+ID2, only insert the new rows Insert all the new rows, ignore inserts that trigger unique constraint violations Any thoughts?

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  • db optimization - have a total field or query table?

    - by Dorian Fife
    I have an app where users get points for actions they perform - either 1 point for an easy action or 2 for a difficult one. I wish to display to the user the total number of points he got in my app and the points obtained this week (since Monday at midnight). I have a table that records all actions, along with their time and number of points. I have two alternatives and I'm not sure which is better: Every time the user sees the report perform a query and sum the points the user got Add two fields to each user that records the number of points obtained so far (total and weekly). The weekly points value will be set to 0 every Monday at midnight. The first option is easier, but I'm afraid that as I'll get many users and actions queries will take a long time. The second option bares the risk of inconsistency between the table of actions and the summary values. I'm very interested in what you think is the best alternative here. Thanks, Dorian

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  • References/walkthroughs for maintaining database schemas with Visual Studio 2010?

    - by user206356
    I have Visual Studio 2010 Beta 2 and SQL Server 2008 installed. I'm working with a populated database and want to modify various column types. SQL Server Management Studio requires me to drop tables to do this, and get pretty finicky given my moderate level of knowledge of SQL Server. However, I heard the new database project type supports changing the database schema to the desired format and it will handle creating and running all the scripts to implement the changes. I've created a VS2010 database project using the existing database as the source, but so far haven't had much luck figuring out the appropriate method to make the changes without getting an error. As a result, I'm looking for any reference info I can find on using VS2010's capabilities in this area. Any suggestions?

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  • Is this safe? Is this OK to do in MYSQL?

    - by alex
    I have always done this: mysqldump -hlocalhost -uuser -ppass MYDATABASE > /home/f/db_backup/MYDATABASE.sql mysql -uuser -ppass MYDATABASE < MYDATABASE.sql But, if I do this instead...is this safe? Is this identical to the above??? mysqldump -hlocalhost -uuser -ppass MYDATABASE | gzip > /home/f/db_backup/MYDATABASE.sql.gz zcat MYDATABASE.sql.gz | mysql -uuser -ppass MYDATABASE

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  • Has inheritance become bad?

    - by mafutrct
    Personally, I think inheritance is a great tool, that, when applied reasonably, can greatly simplify code. However, I seems to me that many modern tools dislike inheritance. Let's take a simple example: Serialize a class to XML. As soon as inheritance is involved, this can easily turn into a mess. Especially if you're trying to serialize a derived class using the base class serializer. Sure, we can work around that. Something like a KnownType attribute and stuff. Besides being an itch in your code that you have to remember to update every time you add a derived class, that fails, too, if you receive a class from outside your scope that was not known at compile time. (Okay, in some cases you can still work around that, for instance using the NetDataContract serializer in .NET. Surely a certain advancement.) In any case, the basic principle still exists: Serialization and inheritance don't mix well. Considering the huge list of programming strategies that became possible and even common in the past decade, I feel tempted to say that inheritance should be avoided in areas that relate to serialization (in particular remoting and databases). Does that make sense? Or am messing things up? How do you handle inheritance and serialization?

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  • getting smallest of coordinates that differ by N or more in Python

    - by user248237
    suppose I have a list of coordinates: data = [[(10, 20), (100, 120), (0, 5), (50, 60)], [(13, 20), (300, 400), (100, 120), (51, 62)]] and I want to take all tuples that either appear in each list in data, or any tuple that differs from all tuples in lists other than its own by 3 or less. How can I do this efficiently in Python? For the above example, the results should be: [[(100, 120), # since it occurs in both lists (10, 20), (13, 20), # since they differ by only 3 (50, 60), (51, 60)]] (0, 5) and (300, 400) would not be included, since they don't appear in both lists and are not different from elements in lists other than their own by 3 or less. how can this be computed? thanks.

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  • Any way to make this PostgreSQL count query any faster?

    - by Ben Dauphinee
    I'm running a case-insensitive search on a table with 7.2 million rows, and I was wondering if there was any way to make this query any faster? Currently, it takes approx 11.6 seconds to execute, with just one search parameter, and I'm worried that as soon as I add more than one, this query will become massively slow. SELECT count(*) FROM "exif_parse" WHERE (description ~* 'canon')

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  • How to translate this query:

    - by xRobot
    How can I translate this 2 queries in postgresql ? : . CREATE TABLE example ( id int(10) unsigned NOT NULL auto_increment, from varchar(255) NOT NULL default '0', message text NOT NULL, lastactivity timestamp NULL default '0000-00-00 00:00:00', read int(10) unsigned NOT NULL, PRIMARY KEY (id), KEY from (from) ) DEFAULT CHARSET=utf8; . SELECT * FROM table_1 LEFT OUTER JOIN table_2 ON ( table_1.id = table_2.id ) WHERE (table_1.lastactivity > NOW()-100);

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  • PhpMyAdmin; Should I disable root login?

    - by Camran
    I have this setup in Phpmyadmin: USER HOST PASSW PRIVILEGES GRANT debian-sys-maint localhost Yes ALL PRIVILEGES YES phpmyadmin localhost Yes USAGE NO root 127.0.0.1 Yes ALL PRIVILEGES YES root localhost Yes ALL PRIVILEGES YES root my_hostname Yes ALL PRIVILEGES YES username localhost Yes ALL PRIVILEGES YES Where "username" is my username and "my_hostname" is my hostname. I am currently only logging in as the last one (username, localhost). Also, I have php which also uses the last ones login details. Should I disable the other ones? And, what other security measures should I take? BTW: My server is Linux and I have root access. Thanks

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  • I built my rails app with sqlite and without specifying any db field sizes, Is my app now foobared for production?

    - by Tim Santeford
    I've been following a lot of good tutorials on building rails apps but I seem to be missing the whole specifying and validating db field sizes part. I love not needing to have to think about it when roughing out an app (I would have never done this with a PHP or ASP.net app). However, now that I'm ready to go to production, I think I might have done myself a disservice by not specifying field sizes as I went. My production db will be MySQL. What is the best practice here? Do I need to go through all of my migration files and specify sizes, update all the models with validation, and update all my form partial views with input max widths? or am I missing a critical step in my development process?

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  • What's the most simple way to retrieve all data from a table and save it back in .NET 3.5?

    - by zoman
    I have a number of tables containing some basic (business related) mapping data. What's the most simple way to load the data from those tables, then save the modified values back. (all data should be replaced in the tables) An ORM is out of question as I would like to avoid creating domain objects for each table. The actual editing of the data is not an issue. (it is exported into Excel where the data is edited, then the file is uploaded with the modified data) The technology is .NET 3.5 (ASP.NET MVC) and SQL Server 2005. Thanks.

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  • About curse of dimensionality

    - by Dan
    My question is about this topic I've been reading about a bit. Basically my understanding is that in higher dimensions all points end up being very close to each other. The doubt I have is whether this means that calculating distances the usual way (euclidean for instance) is valid or not. If it were still valid, this would mean that when comparing vectors in high dimensions, the two most similar wouldn't differ much from a third one even when this third one could be completely unrelated. Is this correct? Then in this case, how would you be able to tell whether you have a match or not?

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  • How to handle ids and polymorphic associations in views if compound keys are not supported?

    - by duncan
    I have a Movie plan table: movie_plans (id, description) Each plan has items, which describe a sequence of movies and the duration in minutes: movie_plan_items (id, movie_plan_id, movie_id, start_minutes, end_minutes) A specific instance of that plan happens in: movie_schedules (id, movie_plan_id, start_at) However the schedule items can be calculated from the movie_plan_items and the schedule start time by adding the minutes create view movie_schedule_items as select CONCAT(p.id, '-', s.id) as id, s.id as movie_schedule_id, p.id as movie_plan_item_id, p.movie_id, p.movie_plan_id, (s.start_at + INTERVAL p.start_minutes MINUTE) as start_at, (s.start_at + INTERVAL p.end_minutes MINUTE) as end_at from movie_plan_items p, movie_schedules s where s.movie_plan_id=p.movie_plan_id; I have a model over this view (readonly), it works ok, except that the id is right now a string. I now want to add a polymorphic property (like comments) to various of the previous tables. Therefore for movie_schedule_items I need a unique and persistent numeric id. I have the following dilemma: I could avoid the id and have movie_schedule_items just use the movie_plan_id and movie_schedule_id as a compound key, as it should. But Rails sucks in this regard. I could create an id using String#hash or a md5, thus making it slower or collision prone (and IIRC String#hash is no longer persistent across processes in Ruby 1.9) Any ideas on how to handle this situation?

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  • Beginner having difficulty with SQL query

    - by Vulcanizer
    Hi, I've been studying SQL for 2 weeks now and I'm preparing for an SQL test. Anyway I'm trying to do this question: For the table: 1 create table data { 2 id int, 3 n1 int not null, 4 n2 int not null, 5 n3 int not null, 6 n4 int not null, 7 primary key (id) 8 } I need to return the relation with tuples (n1, n2, n3) where all the corresponding values for n4 are 0. The problem asks me to solve it WITHOUT using subqueries(nested selects/views) It also gives me an example table and the expected output from my query: 01 insert into data (id, n1, n2, n3, n4) 02 values (1, 2,4,7,0), 03 (2, 2,4,7,0), 04 (3, 3,6,9,8), 05 (4, 1,1,2,1), 06 (5, 1,1,2,0), 07 (6, 1,1,2,0), 08 (7, 5,3,8,0), 09 (8, 5,3,8,0), 10 (9, 5,3,8,0); expects (2,4,7) (5,3,8) and not (1,1,2) since that has a 1 in n4 in one of the cases. The best I could come up with was: 1 SELECT DISTINCT n1, n2, n3 2 FROM data a, data b 3 WHERE a.ID <> b.ID 4 AND a.n1 = b.n1 5 AND a.n2 = b.n2 6 AND a.n3 = b.n3 7 AND a.n4 = b.n4 8 AND a.n4 = 0 but I found out that also prints (1,1,2) since in the example (1,1,2,0) happens twice from IDs 5 and 6. Any suggestions would be really appreciated.

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  • How to translate this 2 queries from Mysql to Postgresql? :

    - by xRobot
    How can I translate this 2 queries in postgresql ? : CREATE TABLE `example` ( `id` int(10) unsigned NOT NULL auto_increment, `from` varchar(255) NOT NULL default '0', `message` text NOT NULL, `lastactivity` timestamp NULL default '0000-00-00 00:00:00', `read` int(10) unsigned NOT NULL, PRIMARY KEY (`id`), KEY `from` (`from`) ) DEFAULT CHARSET=utf8; Query: SELECT * FROM table_1 LEFT OUTER JOIN table_2 ON ( table_1.id = table_2.id ) WHERE (table_1.lastactivity > NOW()-100);

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  • how to get result from this data.

    - by Shantanu Gupta
    I want to compute result from this table. I want quantity 1 - quantity2 as another column in the table shown below. this table has more such records I am trying to query but not been able to get result. select * from v order by is_active desc, transaction_id desc PK_GUEST_ITEM_ID FK_GUEST_ID QUANTITY TRANSACTION_ID IS_ACTIVE ---------------- -------------------- ---------------------- -------------------- ----------- 12963 559 82000 795 1 12988 559 79000 794 0 12987 559 76000 793 0 12986 559 73000 792 0 12985 559 70000 791 0 12984 559 67000 790 0 12983 559 64000 789 0 12982 559 61000 788 0 12981 559 58000 787 0 12980 559 55000 786 0 12979 559 52000 785 0 12978 559 49000 784 0 12977 559 46000 783 0 12976 559 43000 782 0 I want another column that will contain the subtraction of two quantities . DESIRED RESULT SHOULD BE SOMETHING LIKE THIS PK_GUEST_ITEM_ID FK_GUEST_ID QUANTITY Result TRANSACTION_ID IS_ACTIVE ---------------- -------------------- ---------------------- -------------------- ----------- 12963 559 82000 3000 795 1 12988 559 79000 3000 794 0 12987 559 76000 3000 793 0 12986 559 73000 3000 792 0 12985 559 70000 3000 791 0 12984 559 67000 3000 790 0 12983 559 64000 3000 789 0 12982 559 61000 3000 788 0 12981 559 58000 3000 787 0 12980 559 55000 3000 786 0 12979 559 52000 3000 785 0 12978 559 49000 3000 784 0 12977 559 46000 3000 783 0 12976 559 43000 NULL 782 0

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  • Table naming convention?

    - by MattSlay
    In our manufacturing shop, each Employee hits the time clock every time they change Jobs or Machines (work centers) during their work day. Each record created in the Time Clock app has foreign keys that link the record to: the Employee, the Job, and the Machine which they are about to operate. I’m trying to determine the best name for this table… If I were tempted to call it ClockRecords or TimeClockRecords, why wouldn’t I also consider naming it JobTimeRecords, or why not MachineTimeRecords. Any ideas on a good name?

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  • Using SQL Server for web applications

    - by rem
    As far as I understand, due to license reqirements all web applications, which use MS SQL Server, use SQL Server Express (free) or SQL Server web edition (processor license). Is it so? What are other specific features of SQL Server usage for web app?

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  • How can an improvement to the query cache be tracked?

    - by Bill Paetzke
    I am parameterizing my web app's ad hoc sql. As a result, I expect the query plan cache to reduce in size and have a higher hit ratio. Perhaps even other important metrics will be improved. Could I use perfmon to track this? If so, what counters should I use? If not perfmon, how could I report on the impact of this change?

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