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  • Which Oracle table uses a sequence?

    - by Jaú
    Having a sequence, I need to find out which table.column gets its values. As far as I know, Oracle doesn't keep track of this relationship. So, looking up for the sequence in source code would be the only way. Is that right? Anyone knows of some way to find out this sequence-table relationship?

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  • How do I get save (no exclamation point) semantics in an ActiveRecord transaction?

    - by James A. Rosen
    I have two models: Person and Address which I'd like to create in a transaction. That is, I want to try to create the Person and, if that succeeds, create the related Address. I would like to use save semantics (return true or false) rather than save! semantics (raise an ActiveRecord::StatementInvalid or not). This doesn't work because the user.save doesn't trigger a rollback on the transaction: class Person def save_with_address(address_options = {}) transaction do self.save address = Address.build(address_options) address.person = self address.save end end end (Changing the self.save call to an if self.save block around the rest doesn't help, because the Person save still succeeds even when the Address one fails.) And this doesn't work because it raises the ActiveRecord::StatementInvalid exception out of the transaction block without triggering an ActiveRecord::Rollback: class Person def save_with_address(address_options = {}) transaction do save! address = Address.build(address_options) address.person = self address.save! end end end The Rails documentation specifically warns against catching the ActiveRecord::StatementInvalid inside the transaction block. I guess my first question is: why isn't this transaction block... transacting on both saves?

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  • Which is better practice: complex SQL statements or Recordset manipulation in Access VBA?

    - by mazi
    I'm doing some VBA development and I found creating SQLs quite efficient way of getting everything done (selecting and updating). But I got to this stage where my SQL statements contain complex Switches and WHERE conditions where I have another Selects to update appropriate records. Therefore, I create this SQLs and I simply run it via "CurrentDb.Execute strSQL" and it does everything fine. The question is, why would I declare ADODB.connections etc, set recordsets, loop through it and manipulate the data one by one?

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  • Question About DateCreated and DateModified Columns - SQL Server

    - by user311509
    CREATE TABLE Customer ( customerID int identity (500,20) CONSTRAINT . . dateCreated datetime DEFAULT GetDate() NOT NULL, dateModified datetime DEFAULT GetDate() NOT NULL ); When i insert a record, dateCreated and dateModified gets set to default date/time. When i update/modify the record, dateModified and dateCreated remains as is? What should i do? Obviously, i need to dateCreated value to remain as was inserted the first time and dateModified keeps changing when a change/modification occurs in the record fields. In other words, can you please write a sample quick trigger? I don't know much yet...

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  • Solr; "rookie" question

    - by Camran
    I have a SolrPhpClient on my classifieds website, and whenever users wants to add/remove classified the index in Solr gets updated via Php code. So I wonder, does this mean that my Solr index is open for anybody to alter with? Same Q applies to the Solr Admin page. If I set a password for the admin page, does this mean that my classifieds website wont have access to updating/removing documents from the Solr index? Thanks

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  • Comparing COUNT values within a query?

    - by outsyncof
    I have the following tables in a relation: person(ssn,sex) employment(ssn,workweeksperyear) assume ssn is a key. My assignment was to do this: Given as input the number of weeks per year a person has worked, determine whether there are more males than females who work more weeks than the input value. SELECT COUNT(sex) AS NumMales FROM person WHERE sex = 'Male' AND ssn IN (SELECT ssn FROM employment WHERE workweeksperyear > 48); The above query gets me the number of males for an input value and I could do the same for number of females but how do I compare the 2 results? Any help will be greatly appreciated!

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  • Why connection in Python's DB-API does not have "begin" operation?

    - by newtover
    Working with cursors in mysql-python I used to call "BEGIN;", "COMMIT;", and "ROLLBACK;" explicitly as follows: try: cursor.execute("BEGIN;") # some statements cursor.execute("COMMIT;") except: cursor.execute("ROLLBACK;") then, I found out that the underlying connection object has the corresponding methods: try: cursor.connection.begin() # some statements cursor.connection.commit() except: cursor.connection.rollback() Inspecting the DB-API PEP I found out that it does not mention the begin() method for the connection object, even for the extensions. Mysql-python, by the way, throws the Deprecation Warning, when you use the method. sqlite3.connection, for example, does not have the methd at all. And the question is why there is no such method in the PEP? Is the statement somehow optional, is it enough to invoke commit() instead?

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  • Systems design question: DB connection management in load-balanced n-tier

    - by aoven
    I'm wondering about the best approach to designing a DB connection manager for a load-balanced n-tier system. Classic n-tier looks like this: Client -> BusinessServer -> DBServer A load-balancing solution as I see it would then look like this: +--> ... +--+ +--> BusinessServer +--+--> SessionServer --+ Client -> Gateway --+--> BusinessServer +--| +--> DBServer +--> BusinessServer +--+--------------------+ +--> ... +--+ As pictured, the business server component is being load-balanced via multiple instances, and a hardware gateway is distributing the load among them. Session server probably needs to be situated outside the load-balancing array, because it manages state, which mustn't be duplicated. Barring any major errors in design so far, what is the best way to implement DB connection management? I've come up with a couple of options, but there may be others I'm not aware of: Introduce a new Broker component between the DBServer and the other components and let it handle the DB connections. The upside is that all the connections can be managed from a single point, which is very convenient. The downside is that now there is an additional "single point of failure" in the system. Other components must go through it for every request that involves DB in some way, which also makes this a bottleneck. Move the DB connection management into BusinessServer and SessionServer components and let each handle its own DB connections. The upside is that there is no additional "single point of failure" or bottleneck components. The downside is that there is also no control over possible conflicts and deadlocks apart from what DBServer itself can provide. What else can be done? FWIW: Technology is .NET, but none of the vendor-specific stacks are used (e.g. no WCF, MSMQ or the like).

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  • Is it a good practice to implement aggregate routes in Entity Framework 4?

    - by Kohan
    Having just started working on a new project using Entity Framework 4, I spoke to some of the other team that use NHibernate for advice. They implement aggregate routes on their entities, so instead of adding an order through the orders entity, they would add it through customer.order by having an addOrder method on customer. This is the approach I have taken but I am, alas, running into problems. These are issues that I hope to work out, but it got me thinking ... Is this a good way to work or am I fighting an uphill battle unnecessarily?

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  • Dynamic data validation in ASP.NET MVC

    - by user252160
    I've recently read about the model validation capabilities of ASP.NET MVC which are all very cool until a certain point. What happens if the application doesn't know the data that it works with because it is all stored in DB and built together at runtime. Just like in Drupal, I'd like to be able to define custom types at runtime, and assign runtime validation rules as well. Obviously, the idea of assigning attributes to well established models is now gone. What else could be done ? I am thinking in terms of rules being stored as JSON objects in the DB fields or something like that.

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  • Question About DateCreated and DateModified Columns - MS SQL Server

    - by user311509
    CREATE TABLE Customer ( customerID int identity (500,20) CONSTRAINT . . dateCreated datetime DEFAULT GetDate() NOT NULL, dateModified datetime DEFAULT GetDate() NOT NULL ); When i insert a record, dateCreated and dateModified gets set to default date/time. When i update/modify the record, dateModified and dateCreated remains as is? What should i do? Obviously, i need to dateCreated value to remain as was inserted the first time and dateModified keeps changing when a change/modification occurs in the record fields. In other words, can you please write a sample quick trigger? I don't know much yet... Any help will be appreciated.

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  • Yahoo Query Language Problem

    - by Damiano
    Hello everybody! Today, I've started with Yahoo Query Language. I would use it to retrive stocks details, so I'm talking about Yahoo Finance. I think there is a bug on this language. This is my query: select * from yahoo.finance.quoteslist where symbol='@^GSPC' I ALWAYS get 51 results! it's impossible, take a look at: http://it.finance.yahoo.com/q/cp?s=^GSPC There are 500 results! I also tried some paging parameters. select * from yahoo.finance.quoteslist(50,30) where symbol='@^GSPC' (to get from 50 to 80) select * from yahoo.finance.quoteslist(100) where symbol='@^GSPC' (to get the first 100 results) select * from yahoo.finance.quoteslist where symbol='@^GSPC' limit 30 offset 50 but ALWAYS the last stock is: <quote symbol="BBY"> <Symbol>BBY</Symbol> <LastTradePriceOnly>41.03</LastTradePriceOnly> <LastTradeDate>5/7/2010</LastTradeDate> <LastTradeTime>4:00pm</LastTradeTime> <Change>-0.48</Change> <Open>41.35</Open> <DaysHigh>42.35</DaysHigh> <DaysLow>39.60</DaysLow> <Volume>14129531</Volume> </quote> Why do I have this kind of problem? Thank you so much for your support! (P.S. I've tested it on Yahoo YQL console)

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  • Any difference in performance/compatibility of different languages in PostgreSQL?

    - by Igor
    In nowadays the PostgreSQL offers plenty of procedural languages: pl/pgsql, pl/perl, etc Are there any difference in the speed/memory consumption in procedures written in different languages? Does anybody have done any test? Is it true that to use the native pl/pgsql is the most correct choice? How the procedure written in C++ and compiled into loadable module differs in all parameter w.r.t. the user function written with pl/* languages?

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  • How to handle large dataset with JPA (or at least with Hibernate)?

    - by Roman
    I need to make my web-app work with really huge datasets. At the moment I get either OutOfMemoryException or output which is being generated 1-2 minutes. Let's put it simple and suppose that we have 2 tables in DB: Worker and WorkLog with about 1000 rows in the first one and 10 000 000 rows in the second one. Latter table has several fields including 'workerId' and 'hoursWorked' fields among others. What we need is: count total hours worked by each user; list of work periods for each user. The most straightforward approach (IMO) for each task in plain SQL is: 1) select Worker.name, sum(hoursWorked) from Worker, WorkLog where Worker.id = WorkLog.workerId group by Worker.name; //results of this query should be transformed to Multimap<Worker, Long> 2) select Worker.name, WorkLog.start, WorkLog.hoursWorked from Worker, WorkLog where Worker.id = WorkLog.workerId; //results of this query should be transformed to Multimap<Worker, Period> //if it was JDBC then it would be vitally //to set resultSet.setFetchSize (someSmallNumber), ~100 So, I have two questions: how to implement each of my approaches with JPA (or at least with Hibernate); how would you handle this problem (with JPA or Hibernate of course)?

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  • Calling data from different model in Rails

    - by Danny McClelland
    Hi Everyone, I need to be able to call data from a different model - not just one field, but any of them. At the moment I have the following models: kase person company party I can call information from the company to the kase and from the person to the kase using this: <li>Client Company Address: <span class="address"><%=h @kase.company.companyaddress %></span></li> <li>Case Handler: <span><%=h @kase.person.personname %></span></li> Those two work, however if I add the following: <li>Client Company Fax: <span><%=h @kase.company.companyfax %></span></li> <li>Case Handler Tel: <span><%=h @kase.person.personmobile %></span></li> <li>Case Handler Email: <span><%=h @kase.person.personemail %></span></li> Any idea whats wrong? Thanks, Danny EDIT: I get the following error message: NoMethodError in Kases#show Showing app/views/kases/show.html.erb where line #37 raised: You have a nil object when you didn't expect it! The error occurred while evaluating nil.personname The lines that are noted are as follows: 34: <div id="clientinfo_showhide" style="display:none"> 35: <li>Client Company Address: <span class="address"><%=h @kase.company.companyaddress %></span></li> 36: <li>Client Company Fax: <span><%=h @kase.company.companyfax %></span></li> 37: <li>Case Handler: <span><%=h @kase.person.personname %></span></li> 38: <li>Case Handler Tel: <span><%=h @kase.person.personmobile %></span></li> 39: <li>Case Handler Email: <span><%=h @kase.person.personemail %></span></li> 40: </div> The model for the kase is as follows: class Kase belongs_to :company # foreign key: company_id belongs_to :person # foreign key in join table The model for the person is as follows: class Person has_many :kases # foreign key in join table belongs_to :company The model for the company is as follows: class Company has_many :kases has_many :people def to_s; companyname; end Hope this helps!

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  • Combining cache methods - memcache/disk based

    - 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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  • MS Access 2003 - Failure to create MDE file: error VBA is corrupt?

    - by Justin
    Ok so this is a brand new snag I have run into. I am trying to launch a new MDE from my source MDB file, and it is locking up Access. So in my mdb, I am first compacting and repairing, and then selecting create a new mde (just as I have done many times before). It looks like it is starting the process, but never gets to where it compacts when it is done, and access is not responding. So after I force close the app, I look in the folder where I am trying to create the MDE to and I see there is a new access db1 file there. If I try to open that it gives me an error that says file not found, and then it says the Visual Basic for Applications is corrupt. The thing is, I just made a very simple adjustment to the code since last launching an mde, and after this I double and triple checked it...its not that because its just a simple open this form and close this one addition. I did however have my source mdb file on a disc that I copied to my laptop, and then tried to re link the tables to the network drive (had them linked to other tables on my local drive so that I could develop offline)?? PLEASE HELP!!!

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  • I am not able to drop foreign key in mysql Error 150. Please help

    - by Shantanu Gupta
    i am trying to create a foreign key in my table. But when i executes my query it shows me error 150 Error Code : 1005 Can't create table '.\vts#sql-6ec_1.frm' (errno: 150) (0 ms taken) My Queries are Query to create a foreign Key alter table `vts`.`tblguardian` add constraint `FK_tblguardian` FOREIGN KEY (`GuardianPickPointId`) REFERENCES `tblpickpoint` (`PickPointId`) EDIT: Now I am trying to drop this constraint But it fails again and shows me same error as it was giving when i was trying to create foreign key. alter table `vts`.`tblguardian` drop index `FK_tblguardian` Primary Key table CREATE TABLE `tblpickpoint` ( `PickPointId` int(4) NOT NULL auto_increment, `PickPointName` varchar(500) default NULL, `PickPointLabel` varchar(500) default NULL, `PickPointLatLong` varchar(100) NOT NULL, PRIMARY KEY (`PickPointId`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 CHECKSUM=1 DELAY_KEY_WRITE=1 ROW_FORMAT=DYNAMIC Foreign Key Table CREATE TABLE `tblguardian` ( `GuardianId` int(4) NOT NULL auto_increment, `GuardianName` varchar(500) default NULL, `GuardianAddress` varchar(500) default NULL, `GuardianMobilePrimary` varchar(15) NOT NULL, `GuardianMobileSecondary` varchar(15) default NULL, `GuardianPickPointId` int(4) default NULL, PRIMARY KEY (`GuardianId`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1

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  • Alternative design for a synonyms table?

    - by Majid
    I am working on an app which is to suggest alternative words/phrases for input text. I have doubts about what might be a good design for the synonyms table. Design considerations: number of synonyms is variable, i.e. football has one synonym (soccer), but in particular has two (particularly, specifically) if football is a synonym to soccer, the relation exists in the opposite direction as well. our goal is to query a word and find its synonyms we want to keep the table small and make adding new words easy What comes to my mind is a two column design with col a = word and col b = delimited list of synonyms Is there any better alternative? What about using two tables, one for words and the other for relations?

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  • Update MySQL table from jsp

    - by vishnu
    I have these in a jsp file. But these values are not updated in the mysql table. May be it is not commiting. How can i solve this ? String passc1 = request.getParameter("passc1"); String accid = request.getParameter("accid"); int i = 0; String sql = " update customertb " + " set passwd = ?" + " where acc_no = ?;"; try { PreparedStatement ps = con.prepareStatement(sql); ps.setString(1, passc1); ps.setString(2, accid); i = ps.executeUpdate(); } catch (Exception e) { // do something with Exception here. Maybe just throw it up again } finally { con.close(); }

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  • How to use Data aware controls "correctly"?

    - by lyborko
    Hi, I would like to ask experienced users, if you prefer to use data aware controls to add, insert, delete and edit data in DB or you favor to do it manualy. I developed some DB applications, in which for the sake of "user friendly policy" I run into complicated web of table events (afterinsert, afteredit, after... and beforeedit, beforeinsert, before...). After that it was a quite nasty work to debug the application. Aware of this risk (later by another application) I tried to avoid this problem, so I paid increased attention to write code well, readable and comprehensive. It seemed everything all right from the beginning, but as I needed to handle some preprocessing stuff before sending and loading data etc, I run into the same problems again, "slowly and inevitably". Sometime I could not use dataaware controls anyway, and what seemed to be a "cool" feature of DAControl at the beginning it turned to an obstacle on the end. I "had to" write special routine for non-dataaware controls, in order to behave as dataaware. Then I asked myself, why on earth should I use dataaware controls? Is it better to found application architecture on non-dataaware controls? It requires more time to write bug-proof code, of course, but does it worth of it? I do not know... I happened to me several times, like jinxed : paradise on the beginning hell on the end... I do not know, if I use wrong method to write DB program, if there is some standard common practice how to proceed. Or if it is common problem to everybody? Thanx for advices and your experiences

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  • PHP: table structure

    - by A3efan
    I'm developing a website that has some audio courses, each course can have multiple lessons. I want to display each course in its own table with its different lessons. This is my sql statement: Table: courses id, title Table: lessons id, cid (course id), title, date, file $sql = "SELECT lessons.*, courses.title AS course FROM lessons INNER JOIN courses ON courses.id = lessons.cid GROUP BY lessons.id ORDER BY lessons.id" ; Can someone help me with the PHP code? This is the I code I have written: mysql_select_db($database_config, $config); mysql_query("set names utf8"); $sql = "SELECT lessons.*, courses.title AS course FROM lessons INNER JOIN courses ON courses.id = lessons.cid GROUP BY lessons.id ORDER BY lessons.id" ; $result = mysql_query($sql) or die(mysql_error()); while ($row = mysql_fetch_assoc($result)) { echo "<p><span class='heading1'>" . $row['course'] . "</span> </p> "; echo "<p class='datum'>Posted onder <a href='*'>*</a>, latest update on " . strftime("%A %d %B %Y %H:%M", strtotime($row['date'])); } echo "</p>"; echo "<class id='text'>"; echo "<p>...</p>"; echo "<table border: none cellpadding='1' cellspacing='1'>"; echo "<tr>"; echo "<th>Nr.</th>"; echo "<th width='450'>Lesso</th>"; echo "<th>Date</th>"; echo "<th>Download</th>"; echo "</tr>"; echo "<tr>"; echo "<td>" . $row['nr'] . "</td>"; echo "<td>" . $row['title'] . "</td>"; echo "<td>" . strftime("%d/%m/%Y", strtotime($row['date'])) . "</td>"; echo "<td><a href='audio/" . rawurlencode($row['file']) . "'>MP3</a></td>"; echo "</tr>"; echo "</table>"; echo "<br>"; } ?>

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  • SQLAlchemy - relationship limited on more than just the foreign key

    - by Marian
    I have a wiki db layout with Page and Revisions. Each Revision has a page_id referencing the Page, a page relationship to the referenced page; each Page has a all_revisions relationship to all its revisions. So far so common. But I want to implement different epochs for the pages: If a page was deleted and is recreated, the new revisions have a new epoch. To help find the correct revisions, each page has a current_epoch field. Now I want to provide a revisions relation on the page that only contains its revisions, but only those where the epochs match. This is what I've tried: revisions = relationship('Revision', primaryjoin = and_( 'Page.id == Revision.page_id', 'Page.current_epoch == Revision.epoch', ), foreign_keys=['Page.id', 'Page.current_epoch'] ) Full code (you may run that as it is) However this always raises ArgumentError: Could not determine relationship direction for primaryjoin condition ...`, I've tried all I had come to mind, it didn't work. What am I doing wrong? Is this a bad approach for doing this, how could it be done other than with a relationship?

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