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  • Mysql with innodb and serializable transaction does not (always) lock rows

    - by Tobias G.
    Hello, I have a transaction with a SELECT and possible INSERT. For concurrency reasons, I added FOR UPDATE to the SELECT. To prevent phantom rows, I'm using the SERIALIZABLE transaction isolation level. This all works fine when there are any rows in the table, but not if the table is empty. When the table is empty, the SELECT FOR UPDATE does not do any (exclusive) locking and a concurrent thread/process can issue the same SELECT FOR UPDATE without being locked. CREATE TABLE t ( id INT NOT NULL AUTO_INCREMENT PRIMARY KEY, display_order INT ) ENGINE = InnoDB; SET TRANSACTION ISOLATION LEVEL SERIALIZABLE; START TRANSACTION; SELECT COALESCE(MAX(display_order), 0) + 1 from t FOR UPDATE; .. This concept works as expected with SQL Server, but not with MySQL. Any ideas on what I'm doing wrong? EDIT Adding an index on display_order does not change the behavior.

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  • LAbeling with Percentage in R plot

    - by Libo Cannici
    Hi I have made this function that takes a table and prepare the label for a barplot prepare_labels <- function(ft){ labs <- ft labs <- paste(labs, "\n", sep="") labs <- paste(labs, round(prop.table(ft)*100,2), sep="") labs <- paste(labs, "%", sep="") return(labs) } It actually works fine, but is there any better way to write that function, the above code looks ugly and I want to write beautiful code :-) ex: ft <- table(mydata$phone_partner_products) prepare_labels(ft) [1] "3752\n34.09%" "226\n2.05%" "2907\n26.41%" "1404\n12.76%" "1653\n15.02%" [6] "1065\n9.68%"

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  • [SQL] Getting the sum of several columns from two tables

    - by romaintaz
    I want to get the sum of several columns from 2 different tables (these tables share the same structure). If I only consider one table, I would write this kind of query: SELECT MONTH_REF, SUM(amount1), SUM(amount2) FROM T_FOO WHERE seller = XXX GROUP BY MONTH_REF; However, I would like to also work with the data from the table T_BAR, and then have a select query that return the following columns: MONTH_REF SUM(T_FOO.amount1) + SUM(T_BAR.amount1) SUM(T_FOO.amount2) + SUM(T_BAR.amount2) everything grouped by the value of MONTH_REF. Note that a record for a given MONTH_REF can be found in one table but not in the other table. In this case, I would like to get the sum of T_FOO.amount1 + 0 (or 0 + T_BAR.amount1). How can I write my SQL query to get this information? For information, my database is Oracle 10g.

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  • How would you write this Clojure snippet in Ruby and/or Haskell?

    - by dnolen
    I was working on a Rails template and was trying to write a bit of code that allows me to populate a table or multiple columns of ul tags "top-to-bottom" and "left-to-right" across however many columns I specify. I'm just getting the hang of Ruby so I couldn't figure this out. I'm also curious about an idiomatic Haskell version for this useful snippet. Improvements to Clojure version appreciated: (defn table [xs & {:keys [cols direction] :or {cols 1 direction 'right}}] (into [] (condp = direction 'down (let [c (count xs) q (int (/ c cols)) n (if (> (mod c q) 0) (inc q) q)] (apply map vector (partition n n (repeat nil) xs))) 'right (map vec (partition cols cols (repeat nil) xs))))) With this bit of code I can then do the following: (table (range 10) :cols 3) Printed out this would look like so: 0 1 2 3 4 5 6 7 8 9 And the trickier one: (table (range 10) :cols 3 :direction 'down) Looks like so: 0 4 8 1 5 9 2 6 3 7

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  • continuously fetch data from database using JAVA

    - by deathcaller
    Hi all, I've a scenario where my java program has to continuously communicate with the database table, example my java program has to get the data of my table when new rows are added to it at runtime. There should be continuous communication between my program and database. if the table has 10 rows initially and 2 rows are added by the user, it must detect this and return the rows. My program shouldn't use AJAX and timers. Please Help.

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  • Extendable accessing of sqlite database on android platform

    - by mscriven
    Hi, I am fairly new to the android sdk and databases and have been searching for an answer to this quite some time. I am trying to build an app which has multiple tables within a database. e.g. one for weapons, armours etc. However, my DatabaseManager class which handles all of my table creating, DatabaseHelper inner class and populating of data is creating for an extremely large class requiring high maintenance. Every time I would like to add or remove a table column I need to change quite a few areas of code, - Every reference to the addition of a row in that table with data - The method that the above calls - The method returning all of the database rows - The code in the helper class creating the table - Any specific update methods My question is this: Surely there must be some better way of coding this system, maybe using a database isn't the best way to go, or am i just not used to such large classes having only learned java at university and my largest class consisting of a mere 400-600 lines of code. Thanks for any help!

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  • Best index(es) to use for an OR Statement in SQL Server

    - by Chuck Haines
    I have a table which has a bunch of columns but the two relevant ones are: Due_Amount MONEY Bounced_Due_Amount MONEY I have a SQL query like the following SELECT * FROM table WHERE (Due_Amount 0 OR Bounced_Due_Amount 0) Would the best index to put on this table for SQL Server 2008 be an index which includes both columns in the index, or should I put an separate index on each column?

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  • Debugging (displaying) SQL command sent to the db by SQLAlchemy

    - by morpheous
    I have an ORM class called Person, which wraps around a person table: After setting up the connection to the db etc, I run the ff statement. people = session.query(Person).all() The person table does not contain any data (as yet), so when I print the variable people, I get an empty list. I renamed the table referred to in my ORM class People, to people_foo (which does not exist). I then run the script again. I was surprised that no exception was thrown when attempting to access a table that does not exist. I therefore have the following 2 questions: How may I setup SQLAlchemy so that it propagates db errors back to the script? How may I view (i.e. print) the SQL that is being sent to the db engine If it helps, I am using PostgreSQL as the db

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  • How do i get an instance of the entity type based on MetaTable

    - by dimak
    is there a way to go from a MetaTable to an instance of an entity type so it can be queried with LINQ? What I want to do is this: MetaTable table = GridDataSource.GetTable (); var entity = table.GetInstanceOfEntity(); var test = (from t in entity select t).ToList(); where table.GetInstanceOfEntity() is something that I'm not sure how to implement. Thank you

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  • SQL Select -> product -> comments -> user

    - by user1492716
    thanks for yout time helping on this ;) I'm new to SQL and wish to solve somethign in just one query and i dont know how to do it.- Basically I've a table of products, a table of users and a table of comments, linked by products.id - comments.pid and user.id - comments.uid , i wish to know what is the best practice to create just 1 query and get all products with child comments, including username.

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  • TableView on Tab Bar Application ? Application is crashing.

    - by Andrei
    Steps to reproduce: 1. Create a Tab Bar Application called "TestApp" 2. Add new file, a UIViewController subclass with a XIB user interface called "Table" 3. Open up MainWindows.xib, click on the Second tab bar item and in Inspector change the NIB Name from "SecondView" to "Table". Save and close. 4. Open up Table.xib and drag a TableView on top of the view. Now link the dataSource and delegate outlets of the TableView to the Table.xib File's Owner. 5. Add the following code to Table.m: - (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView { NSLog(@"Returning num sections"); return 1; } - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section { NSLog(@"Returning num rows"); return 1; } - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { NSLog(@"Trying to return cell"); static NSString *CellIdentifier = @"Cell"; UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier]; if (cell == nil) { cell = [[[UITableViewCell alloc] initWithFrame:CGRectZero reuseIdentifier:CellIdentifier] autorelease]; } cell.text = @"Hello"; NSLog(@"Returning cell"); return cell; } 6.Run the application and select the Second tab bar item. If I start with a View-based application, add a TableView to it, link the outlets to the File's owner and add that piece of code it all works just fine. What am I doing wrong ? Why is the application crashing ?

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  • Multiple column foreign key contraints

    - by eugene4968
    I want to setup table constraints for the following scenario and I’m not sure how to do it or if it’s even possible in SQL Server 2005. I have three tables A,B,C. C is a child of B. B will have a optional foreign key(may be null) referencing A. For performance reasons I also want table C to have the same foreign key reference to table A. The constraint on table C should be that C must reference its parent (B) and also have the same foreign key reference to A as its parent. Anyone have any thoughts on how to do this?

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  • An html5 canvas element in the background of my page?

    - by fx42
    Is it possible to have a full screen canvas element in the background of a webpage and "normal" markup elements like a table in front of it? like the following snippet (if it wouldn't be used as alternative content): <canvas id=&#34;imageView&#34; width=100%; height=100%;> <table>...</table> </canvas>

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  • dynamic SQL not working as expected

    - by christine33990
    create or replace procedure createtables Authid current_user as begin execute immediate 'create table newcustomer as select * from customer'; end; create or replace procedure e is begin createtables; select * from newcustomer; end; I got two procedures above. first one will create a new tables called newcustomer, second procedure will call the first procedure and query to the newcustomer table. when I try to compile this code, it says the table is not yet created, I don't really get it as I have called createtables procedure so I assume I have created the table. Any help will be appreciated. Thanks

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  • Joining tables, if percentage is above certain value

    - by CluelessGerman
    My question is similar to this one: Compare rows and get percentage However, little different. I adapted my question to the other post. I got 2 tables. First table: user_id | post_id 1 1 1 2 1 3 2 12 2 15 And second table: post_id | rating 1 1 1 2 1 3 2 1 2 5 3 null 3 1 3 4 12 4 15 1 So now I would like to count the rating for each post, in the second table. If the rating has more than, lets say, 50% positive ratings than I want to get the post_id and going it to the post_id from table one and add 1 to the user_id. At the end it would return the user_id with the number of positive posts. The result for above table would be: user_id | helpfulPosts 1 2 2 1 The post with post_id 1 and 3 have positive rating, because more than 50% have ratings of 1-3. The post with id = 2 is not positive, because the rating is exactly 50%. How would I achieve this? For clarification: It's a mysql rdbm and a positive post, is one where the number of rating_ids with 1, 2 and 3 are more than half of the overall rating. Basically the same thing, from the other thread I posted above.

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  • GROUP BY and SUM distinct date across 2 tables

    - by kenitech
    I'm not sure if this is possible in one mysql query so I might just combine the results via php. I have 2 tables: 'users' and 'billing' I'm trying to group summed activity for every date that is available in these two tables. 'users' is not historical data but 'billing' contains a record for each transaction. In this example I am showing a user's status which I'd like to sum for created date and deposit amounts that I would also like to sum by created date. I realize there is a bit of a disconnect between the data but I'd like to some all of it together and display it as seen below. This will show me an overview of all of the users by when they were created and what the current statuses are next to total transactions. I've tried UNION as well as LEFT JOIN but I can't seem to get either to work. Union example is pretty close but doesn't combine the dates into one row. ( SELECT created, SUM(status) as totalActive, NULL as totalDeposit FROM users GROUP BY created ) UNION ( SELECT created, NULL as totalActive, SUM(transactionAmount) as totalDeposit FROM billing GROUP BY created ) I've also tried using a date lookup table and joining on the dates but the SUM values are being added multiple times. note: I don't care about the userIds at all but have it in here for the example. users table (where status of '1' denotes "active") (one record for each user) created | userId | status 2010-03-01 | 10 | 0 2010-03-01 | 11 | 1 2010-03-01 | 12 | 1 2010-03-10 | 13 | 0 2010-03-12 | 14 | 1 2010-03-12 | 15 | 1 2010-03-13 | 16 | 0 2010-03-15 | 17 | 1 billing table (record created for every instance of a billing "transaction" created | userId | transactionAmount 2010-03-01 | 10 | 50 2010-03-01 | 18 | 50 2010-03-01 | 19 | 100 2010-03-10 | 89 | 55 2010-03-15 | 16 | 50 2010-03-15 | 12 | 90 2010-03-22 | 99 | 150 desired result: created | sumStatusActive | sumStatusInactive | sumTransactions 2010-03-01 | 2 | 1 | 200 2010-03-10 | 0 | 1 | 55 2010-03-12 | 2 | 0 | 0 2010-03-13 | 0 | 0 | 0 2010-03-15 | 1 | 0 | 140 2010-03-22 | 0 | 0 | 150 Table dump: CREATE TABLE IF NOT EXISTS `users` ( `created` date NOT NULL, `userId` int(11) NOT NULL, `status` smallint(6) NOT NULL ) ENGINE=MyISAM DEFAULT CHARSET=latin1; INSERT INTO `users` (`created`, `userId`, `status`) VALUES ('2010-03-01', 10, 0), ('2010-03-01', 11, 1), ('2010-03-01', 12, 1), ('2010-03-10', 13, 0), ('2010-03-12', 14, 1), ('2010-03-12', 15, 1), ('2010-03-13', 16, 0), ('2010-03-15', 17, 1); CREATE TABLE IF NOT EXISTS `billing` ( `created` date NOT NULL, `userId` int(11) NOT NULL, `transactionAmount` int(11) NOT NULL ) ENGINE=MyISAM DEFAULT CHARSET=latin1; INSERT INTO `billing` (`created`, `userId`, `transactionAmount`) VALUES ('2010-03-01', 10, 50), ('2010-03-01', 18, 50), ('2010-03-01', 19, 100), ('2010-03-10', 89, 55), ('2010-03-15', 16, 50), ('2010-03-15', 12, 90), ('2010-03-22', 99, 150);

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  • MYSQL - SQL query Getting single record for the similar records and populating other columns with which has more length

    - by Bujji
    Here is my case , I have a database table with below fields name place_code email phone address details estd others and example data if you look at the above example table First three records are talking about XYZ and place code 1020 . I want create a single record for these three records based on substring(name,1,4) place_code ( I am lucky here for all the similar records satisfies this condition and unique in the table .) For the other columns which record column length has max . For example again for the above 3 records email should be [email protected] , phone should be 657890 and details should be "testdetails" This should be done for all the table . (Some has single records and some has max 10 records ) Any help on query that helps me to get the desired result ? Thank You Regards Kiran

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  • Jquery .text() call returns null?

    - by Alex
    Hey all, I'm practicing Jquery and I've written this simple Jquery statement: var someText = $("table tr td").text(); Should this not return all text of td elements found within tr's that are found within tables? How do I fix this? Currently when I run this, it says that table tr td is null, but I have a table on the page I'm testing on. Thanks!

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  • Adding a Image to UITable View Cell

    - by Graeme
    Hi, I have a table in which I want a dynamic image to load in at the left-hand side. The table needs to use an IF statement to select the appropriate image from the "Resources" folder, and needs to be based upon [dog types]. The [dog types] is extracted from an RSS feed, and so the image in the table cell needs to match the each cell's [dog types] tag. I suspect I need to use - (UIImage *)imageForTypes:(NSString *)types { to do such a thing. Thanks.

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  • Rails - inheritance hierarchy of classes where a subtype can play two roles

    - by Miquel
    I need to model Owners and Rentees in an application, so you have stuff that is always owned by someone and can be rented for someone else. I first approached this problem with Single Table Inheritance because both types of person will share all attributes, so you would have a model called Person associated to a table people with Owner and Rentee inheriting from Person. The problem is that Single type inheritance discerns subtypes using a field type and therefore a record in the table can represent either an Owner or a Rentee but not both at the same time, while in the real context you can have an Owner which is renting something from another Owner and therefore that person is at the same time an Owner and a Rentee. How would you approach this problem? Would you use separated tables for owners and rentees? Is there any other type of table inheritance in Rails?

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  • Hibernate violation error

    - by sarah
    Hi All, I am having a designation table with d_name as primary key which i am using in user table as foreign key reference .I am using hbm for mapping in designation hbm i have id defined as d_name mapped to database column .I am getting a error saying "integrity constraint violation(user_designation_fk) parent key not found. " Where am i going wrong /this error is coming while i am tring to add a user selecting a designation reading from designation table.

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  • Should multiple regional websites all use the same database?

    - by John Himmelman
    I'm developing a cms for a company that has multiple regional sites (us, uk, china, russia, etc..). Should I use a separate database for each of these sites or use a single database with a 'site' field in each table? My main concern is the table language encoding (ie, can storing strings in different langauges in the same table cause problems, such as sorting issues).

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  • How to design a database schema for storing text in multiple languages?

    - by stach
    We have a PostgreSQL database. And we have several tables which need to keep certain data in several languages (the list of possible languages is thankfully system-wide defined). For example lets start with: create table blah (id serial, foo text, bar text); Now, let's make it multilingual. How about: create table blah (id serial, foo_en text, foo_de text, foo_jp text, bar_en text, bar_de text, bar_jp text); That would be good for full-text search in Postgres. Just add a tsvector column for each language. But is it optimal? Maybe we should use another table to keep the translations? Like: create table texts (id serial, colspec text, obj_id int, language text, data text); Maybe, just maybe, we should use something else - something out of the SQL world? Any help is appreciated.

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  • Second query to SQLite (on iPhone) errors.

    - by Luke
    Hi all, On the iPhone, I am developing a class for a cart that connects directly to a database. To view the cart, all items can be pulled from the database, however, it seems that removing them doesn't work. It is surprising to me because the error occurs during connection to the database, except not the second time I connect even after the DB has been closed. #import "CartDB.h" #import "CartItem.h" @implementation CartDB @synthesize database, databasePath; - (NSMutableArray *) getAllItems { NSMutableArray *items = [[NSMutableArray alloc] init]; if([self openDatabase]) { const char *sqlStatement = "SELECT * FROM items;"; sqlite3_stmt *compiledStatement; if(sqlite3_prepare_v2(cartDatabase, sqlStatement, -1, &compiledStatement, NULL) == SQLITE_OK) { while(sqlite3_step(compiledStatement) == SQLITE_ROW) { int rowId = sqlite3_column_int(compiledStatement, 0); int productId = sqlite3_column_int(compiledStatement, 1); NSString *features = [NSString stringWithUTF8String:(char *)sqlite3_column_text(compiledStatement, 2)]; int quantity = sqlite3_column_int(compiledStatement, 3); CartItem *cartItem = [[CartItem alloc] initWithRowId:rowId productId:productId features:features quantity:quantity]; [items addObject:cartItem]; [cartItem release]; } } sqlite3_finalize(compiledStatement); } [self closeDatabase]; return items; } - (BOOL) removeCartItem:(CartItem *)item { sqlite3_stmt *deleteStatement; [self openDatabase]; const char *sql = "DELETE FROM items WHERE id = ?"; if(sqlite3_prepare_v2(cartDatabase, sql, -1, &deleteStatement, NULL) != SQLITE_OK) { return NO; } sqlite3_bind_int(deleteStatement, 1, item.rowId); if(SQLITE_DONE != sqlite3_step(deleteStatement)) { sqlite3_reset(deleteStatement); [self closeDatabase]; return NO; } else { sqlite3_reset(deleteStatement); [self closeDatabase]; return YES; } } - (BOOL) openDatabase { if(sqlite3_open([databasePath UTF8String], &cartDatabase) == SQLITE_OK) { return YES; } else { return NO; } } - (void) closeDatabase { sqlite3_close(cartDatabase); } The error occurs on the line where the connection is opened in openDatabase. Any ideas? Need to flush something? Something gets autoreleased? I really can't figure it out. --Edit-- The error that I receive is GDB: Program received signal "EXC_BAD_ACCESS". --Edit-- I ended up just connecting in the init and closing in the free methods, which might not be the proper way, but that's another question altogether so it's effectively persistent instead of connecting multiple times. Still would be nice to know what was up with this for future reference.

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