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  • Concurency problem with Isolation - read-committed

    - by Ratn Deo--Dev
    I have to write a simple demo for amount withdrawl from a joint Bank amount .Andy and Jen holds a joint bank account with number 123 . Suppose they have 100$ in their account .Jen and Andy are operating their account at the same time and both are trying to withdraw 90$ at the time being .My transaction Isolation is set to read-committed and both are able to withdraw money leaving the balance to -(minus)80$ although I have constraint that balance should never be less than 0. I am using hibernate .Is versioning only way to solve this problem or I should go for another Isolation level ?

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  • 1 oracle schema support large reques per day , is this safe ?

    - by Hlex
    I 'm java system designer. As we have large project to do tightly, Those projects are java api without webpage. I design to create general flow engine to support all project. This idea use 1 oracle schema , having general transaction table . And others control routing table. They all nearly complete. But DBA Team concern that he is suffered to maintain very large request to 1 schema. 1 reason is if there are problem is some table. He must offline tablespace to fix. This is problem because all project will be affected. I try to convince by split data of each table to partition by project_code & "month number to delete" . Eaxmple partition: PROJ1_05 PROJ1_06 PROJ1_07 PROJ2_05 PROJ2_06 PROJ2_07 and all transaction table will store on its partition. So, If there are problem on any part of tablespace then he should offline some partition and another project with use same table should able to service Transaction per day should around 10Meg Record per day. Is this a good idea? If I must use 1 schema, what is strategy to do? Do you have any comment?

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  • What is the best scala-like persistence framework available right now?

    - by egervari
    What is the best scala-like persistence framework available right now? Hibernate works, but it's not very scala-like. It insists on using annotations, no-arg constructors, doesn't work with anonymous class instances, doesn't work with scala collections, has an outdated string-based query model, etc. I'm looking for something that really fits Scala. Does it exist? Or do I have to make it?

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  • Complex SQL query... 3 tables and need the most popular in the last 24 hours using timestamps!

    - by Stefan
    Hey guys, I have 3 tables with a column in each which relates to one ID per row. I am looking for an sql statement query which will check all 3 tables for any rows in the last 24 hours (86400 seconds) i have stored timestamps in each tables under column time. After I get this query I will be able to do the next step which is to then check to see how many of the ID's a reoccurring so I can then sort by most popular in the array and limit it to the top 5... Any ideas welcome! :) Thanks in advanced. Stefan

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  • PDO update with conditional?

    - by dmontain
    I have a PDO mysql that updates 3 fields. $update = $mypdo->prepare("UPDATE tablename SET field1=:field1, field2=:field2, field3=:field3 WHERE key=:key"); But I want field3 to be updated only when $update3 = true; Is this possible to accomplish with a single query? I could do it with 2 queries where I update field1 and field2 then check the boolean and update field3 if needed in a separate query. But hopefully there is a way to accomplish this in 1 query?

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  • What are the benefits of left outer join vs nested aggregate selects to find the newest rows in a table?

    - by RenderIn
    I'm doing: select * from mytable y where y.year = (select max(yi.year) from mytable yi where yi.person = y.person) Is that better or worse from a performance aspect than: select y.* from mytable y left outer join mytable y2 on y.year < y2.year and y.person = y2.person where y2.year is null The explain plan/anecdotal evidence is inconclusive so I am wondering if in general one is better than the other.

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  • SQL Backup files, distinguish partial and full backup files

    - by ccook
    I have scheduled backups running through SQL Agent, with Full Backups nightly, and differential backups hourly. Is there a way to determine which of the backup files is the Full backup, and which is the latest differential? Intuitively, it would seem the largest backup within 24 hours is the full, and the latest smaller backup is the partial. However, this isn't robust. Is there a way to probe the backup file to check the backup type? (Preferably in c#)

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  • PostgreSQL 8.3 data types: xml vs varchar

    - by Sejanus
    There's xml data type in Postgres, I never used it before so I'd like to hear opinions. Downsides and upsides vs using regular varchar (or Text) column to store xml. The text I'm going to store is xml, well-formed, UTF-8. No need to search by it (I've read searching by xml is slow). This XML actually is data prepared for PDF generation with Apache FOP. XML can be generated dynamically from data found elsewhere (other Postgres tables), it's stored as is only so that I won't need to generate it twice. Kinda backup#2 for already generated PDF documents. Anything else to know? Good practices, performance, maintenance, etc?

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  • Non-Relational DBMS Design Resources

    - by Matt Luongo
    Hey guys, As a personal project, I'm looking to build a rudimentary DBMS. I've read the relevant sections in Elmasri & Navathe (5ed), but could use a more focused text. The rub is that I want to play with novel non-relational data models. While a lot of E&N was great- indexing implementation details in particular- the more advanced DBMS implementation was only targeted to a relational model. I could also use something a bit more practical and detail-oriented, with real-world recommendations. I'd like to defer staring at DBMS source for a while if I can. Any ideas?

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  • Autoincrement uniqueidentifier in C#

    - by drasto
    Basically I want to use uniqueidentifier in similar way as identity. I don't want to insert values into it, It should just insert values automatically, different value for each row. I'm not able to set autoincrement on columns of type uniqueidentifier(the property 'autoincrement' is set to false and is not editable).

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  • KD-Trees and missing values (vector comparison)

    - by labratmatt
    I have a system that stores vectors and allows a user to find the n most similar vectors to the user's query vector. That is, a user submits a vector (I call it a query vector) and my system spits out "here are the n most similar vectors." I generate the similar vectors using a KD-Tree and everything works well, but I want to do more. I want to present a list of the n most similar vectors even if the user doesn't submit a complete vector (a vector with missing values). That is, if a user submits a vector with three dimensions, I still want to find the n nearest vectors (stored vectors are of 11 dimensions) I have stored. I have a couple of obvious solutions, but I'm not sure either one seem very good: Create multiple KD-Trees each built using the most popular subset of dimensions a user will search for. That is, if a user submits a query vector of thee dimensions, x, y, z, I match that query to my already built KD-Tree which only contains vectors of three dimensions, x, y, z. Ignore KD-Trees when a user submits a query vector with missing values and compare the query vector to the vectors (stored in a table in a DB) one by one using something like a dot product. This has to be a common problem, any suggestions? Thanks for the help.

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  • SQL Select * from multiple tables

    - by zaf
    Using PHP/PDO is it possible to use a wildcard for the columns when a select is done on multiple tables and the returned array keys are fully qualified to avoid column name clash? example: SELECT * from table1, table2; gives: Array keys are 'table1.id', 'table2.id', 'table1.name' etc. I tried "SELECT table1.*,table2.* ..." but the returned array keys were not fully qualified so columns with the same name clashed and were overwritten.

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  • MS Analysis Services OLAP API for Python

    - by Kaloyan Todorov
    I am looking for a way to connect to a MS Analysis Services OLAP cube, run MDX queries, and pull the results into Python. In other words, exactly what Excel does. Is there a solution in Python that would let me do that? Someone with a similar question going pointed to Django's ORM. As much as I like the framework, this is not what I am looking for. I am also not looking for a way to pull rows and aggregate them -- that's what Analysis Services is for in the first place. Ideas? Thanks.

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  • How to make this sub-sub-query work?

    - by Josh Weissbock
    I am trying to do this in one query. I asked a similar question a few days ago but my personal requirements have changed. I have a game type website where users can attend "classes". There are three tables in my DB. I am using MySQL. I have four tables: hl_classes (int id, int professor, varchar class, text description) hl_classes_lessons (int id, int class_id, varchar lessonTitle, varchar lexiconLink, text lessonData) hl_classes_answers (int id, int lesson_id, int student, text submit_answer, int percent) hl_classes stores all of the classes on the website. The lessons are the individual lessons for each class. A class can have infinite lessons. Each lesson is available in a specific term. hl_classes_terms stores a list of all the terms and the current term has the field active = '1'. When a user submits their answers to a lesson it is stored in hl_classes_answers. A user can only answer each lesson once. Lessons have to be answered sequentially. All users attend all "classes". What I am trying to do is grab the next lesson for each user to do in each class. When the users start they are in term 1. When they complete all 10 lessons in each class they move on to term 2. When they finish lesson 20 for each class they move on to term 3. Let's say we know the term the user is in by the PHP variable $term. So this is my query I am currently trying to massage out but it doesn't work. Specifically because of the hC.id is unknown in the WHERE clause SELECT hC.id, hC.class, (SELECT MIN(output.id) as nextLessonID FROM ( SELECT id, class_id FROM hl_classes_lessons hL WHERE hL.class_id = hC.id ORDER BY hL.id LIMIT $term,10 ) as output WHERE output.id NOT IN (SELECT lesson_id FROM hl_classes_answers WHERE student = $USER_ID)) as nextLessonID FROM hl_classes hC My logic behind this query is first to For each class; select all of the lessons in the term the current user is in. From this sort out the lessons the user has already done and grab the MINIMUM id of the lessons yet to be done. This will be the lesson the user has to do. I hope I have made my question clear enough.

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  • ER Data Model - confused by diagram.

    - by Khou
    Hi im a little confused by this diagram http://www.b-eye-network.com/images/content/i030ht0104.gif (Last diagram in the article) 1 - In the "ACCOUNTING ENTRY" table it shows "DebitEntry" and "CreditEntry" i) is this two column or ii) is this two rows of data? or iii) is it two separate tables on its own, Acounting_entry_credit and Accounting_entry_debit? Same question with the "ACCOUNT" table, it shows asset account, livabilities account, equaity account? are they 3 columns or are they 3 rows? Source: http://www.tdan.com/view-articles/5227/

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  • What should be the considerations for choosing SQL/NoSQL?

    - by Yuval A
    Target application is a medium-sized website built to support several hundred-thousand users an hour, with an option to scale above that. Data model is rather simple, and caching potential is pretty high (~10:1 ratio of read to edit actions). What should be the considerations when coming to choose between a relational, SQL-based datastore to a NoSQL option (such as HBase and Cassandra)?

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  • A lock could not obtained within the time requested issue

    - by Wayne Daly
    The title is the error I'm getting, when I click load my program freezes. I assume its because I'm doing a statement inside a statement, but from what I see its the only solution to my issue. By loading I want to just repopulate the list of patients, but to do so I need to do their conditions also. The code works, the bottom method is what I'm trying to fix. I think the issue is that I have 2 statements open but I am not sure. load: public void DatabaseLoad() { try { String Name = "Wayne"; String Pass= "Wayne"; String Host = "jdbc:derby://localhost:1527/Patients"; Connection con = DriverManager.getConnection( Host,Name, Pass); PatientList.clear(); Statement stmt8 = con.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE, ResultSet.CONCUR_UPDATABLE); String SQL8 = "SELECT * FROM PATIENTS"; ResultSet rs8 = stmt8.executeQuery( SQL8 ); ArrayList<PatientCondition> PatientConditions1 = new ArrayList(); while(rs8.next()) { PatientConditions1 = LoadPatientConditions(); } Statement stmt = con.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE, ResultSet.CONCUR_UPDATABLE); String SQL = "SELECT * FROM PATIENTS"; ResultSet rs = stmt.executeQuery( SQL ); while(rs.next()) { int id = (rs.getInt("ID")); String name = (rs.getString("NAME")); int age = (rs.getInt("AGE")); String address = (rs.getString("ADDRESS")); String sex = (rs.getString("SEX")); String phone = (rs.getString("PHONE")); Patient p = new Patient(id, name, age, address, sex, phone, PatientConditions1); PatientList.add(p); } UpdateTable(); UpdateAllViews(); DefaultListModel PatientListModel = new DefaultListModel(); for (Patient s : PatientList) { PatientListModel.addElement(s.getAccountNumber() + "-" + s.getName()); } PatientJList.setModel(PatientListModel); } catch(SQLException err) { System.out.println(err.getMessage()); } } This is the method that returns the arraylist of patient conditions public ArrayList LoadPatientConditions() { ArrayList<PatientCondition> PatientConditionsTemp = new ArrayList(); try { String Name = "Wayne"; String Pass= "Wayne"; String Host = "jdbc:derby://localhost:1527/Patients"; Connection con = DriverManager.getConnection( Host,Name, Pass); Statement stmt = con.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE, ResultSet.CONCUR_UPDATABLE); String SQL = "SELECT * FROM PATIENTCONDITIONS"; ResultSet rs5 = stmt.executeQuery( SQL ); int e = 0; while(rs5.next()) { e++; String ConName = (rs5.getString("CONDITION")); PatientCondition k = new PatientCondition(e,ConName); PatientConditionsTemp.add(k); } } catch(SQLException err) { System.out.println(err.getMessage()); } return PatientConditionsTemp; }

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  • JavaDB/Derby Error 08006

    - by Tom Brito
    In the article Using Java DB in Desktop Applications the Address Book demo have a method disconnect which have a try-catch block that catch and ignores the exception. If you add a printStackTrace you can see that the exception always occur. What's wrong here? The JavaDB should not throw this exception, or they should fix something in the example program?

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  • Weaknesses of Hibernate

    - by Sinuhe
    I would like to know which are the weak points of Hibernate 3. This is not pretended to be a thread against Hibernate. I think it will be a very useful knowledge for decide if Hibernate is the best option for a project or for estimating its time. A weakness can be: A bug Where JDBC or PLSQL are better Performance issues ... Also, can be useful to know some solutions for that problems, better ORM or techniques, or it will be corrected in Hibernate 4. For example, AFAIK, Hibernate will have a very bad performance updating 10000 rows comparing to JDBC in this query: update A set state=3 where state=2

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