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  • Having to insert a record, then update the same record warrants 1:1 relationship design?

    - by dianovich
    Let's say an Order has many Line items and we're storing the total cost of an order (based on the sum of prices on order lines) in the orders table. -------------- orders -------------- id ref total_cost -------------- -------------- lines -------------- id order_id price -------------- In a simple application, the order and line are created during the same step of the checkout process. So this means INSERT INTO orders .... -- Get ID of inserted order record INSERT into lines VALUES(null, order_id, ...), ... where we get the order ID after creating the order record. The problem I'm having is trying to figure out the best way to store the total cost of an order. I don't want to have to create an order create lines on an order calculate cost on order based on lines then update record created in 1. in orders table This would mean a nullable total_cost field on orders for starters... My solution thus far is to have an order_totals table with a 1:1 relationship to the orders table. But I think it's redundant. Ideally, since everything required to calculate total costs (lines on an order) is in the database, I would work out the value every time I need it, but this is very expensive. What are your thoughts?

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  • Most efficient way of checking if Date object and Calendar object are in the same month

    - by Indigenuity
    I am working on a project that will run many thousands of comparisons between dates to see if they are in the same month, and I am wondering what the most efficient way of doing it would be. This isn't exactly what my code looks like, but here's the gist: List<Date> dates = getABunchOfDates(); Calendar month = Calendar.getInstance(); for(int i = 0; i < numMonths; i++) { for(Date date : dates) { if(sameMonth(month, date) .. doSomething } month.add(Calendar.MONTH, -1); } Creating a new Calendar object for every date seems like a pretty hefty overhead when this comparison will happen thousands of times, soI kind of want to cheat a bit and use the deprecated method Date.getMonth() and Date.getYear() public static boolean sameMonth(Calendar month, Date date) { return month.get(Calendar.YEAR) == date.getYear() && month.get(Calendar.MONTH) == date.getMonth(); } I'm pretty close to just using this method, since it seems to be the fastest, but is there a faster way? And is this a foolish way, since the Date methods are deprecated? Note: This project will always run with Java 7

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  • Quickest way to compare a buch of array or list of values.

    - by zapping
    Can you please let me know on the quickest and efficient way to compare a large set of values. Its like there are a list of parent codes(string) and each code has a series of child values(string). The child lists have to be compared with each other and find out duplicates and count how many times they repeat. code1(code1_value1, code1_value2, code3_value3, ..., code1_valueN); code2(code2_value1, code1_value2, code2_value3, ..., code2_valueN); code3(code2_value1, code3_value2, code3_value3, ..., code3_valueN); . . . codeN(codeN_value1, codeN_value2, codeN_value3, ..., codeN_valueN); The lists are huge say like there are 100 parent codes and each has about 250 values in them. There will not be duplicates within a code list. Doing it in java and the solution i could figure out is. Store the values of first set of code in as codeMap.put(codeValue, duplicateCount). The count initialized to 0. Then compare the rest of the values with this. If its in the map then increment the count otherwise append it to the map. The downfall of this is to get the duplicates. Another iteration needs to be performed on a very large list. An alternative is to maintain another hashmap for duplicates like duplicateCodeMap.put(codeValue, duplicateCount) and change the initial hashmap to codeMap.put(codeValue, codeValue). Speed is what is requirement. Hope one of you can help me with it.

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  • SQL Server 2000, how to automate import data from excel

    - by Stan
    Say the source data comes in excel format, below is how I import the data. Converting to csv format via MS Excel Roughly find bad rows/columns by inspecting backup the table that needs to be updated in SQL Query Analyzer truncate the table (may need to drop foreign key constraint as well) import data from the revised csv file in SQL Server Enterprise Manager If there's an error like duplicate columns, I need to check the original csv and remove them I was wondering how to make this procedure more effecient in every step? I have some idea but not complete. For step 2&6, using scripts that can check automatically and print out all error row/column data. So it's easier to remove all errors once. For step 3&5, is there any way to automatically update the table without manually go through the importing steps? Could the community advise, please? Thanks.

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  • Problem with Refreshing data in ExpandableListView

    - by -providerivan.longin1
    Hi! My problem is when I want to refresh data in ExpandableListView while being in that current activity. I create adapter and when I want to add new data to list I call again constructor of that adapter(it is my private variable) with all new data....and then I call onContentChanged() method to redraw my list. But what happens is that I cant expand my list any more...like it is blocked or something and logcat isn't saying anything... This is the code that i call after setting new data in arraylists and maps: mAdapter = new MyExpandableListAdapter( this, groupData, R.layout.contact_list_parent, new String[] { NAME ,NUM_PHOTOS},//NUM_PHOTOS new int[] { R.id.rowText1, R.id.rowText2, R.id.photoAlbumImg }, childData, R.layout.contact_list_child, new String[] { NAME,NUM_PHOTOS}, //NUM_PHOTOS new int[] { R.id.rowText1, R.id.rowText2, R.id.photoAlbumImg } ); this.onContentChanged(); If anyone knows answer to this question please help me:) Thanks.

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  • Long primitive or AtomicLong for a counter?

    - by Rich
    Hi I have a need for a counter of type long with the following requirements/facts: Incrementing the counter should take as little time as possible. The counter will only be written to by one thread. Reading from the counter will be done in another thread. The counter will be incremented regularly (as much as a few thousand times per second), but will only be read once every five seconds. Precise accuracy isn't essential, only a rough idea of the size of the counter is good enough. The counter is never cleared, decremented. Based upon these requirements, how would you choose to implement your counter? As a simple long, as a volatile long or using an AtomicLong? Why? At the moment I have a volatile long but was wondering whether another approach would be better. I am also incrementing my long by doing ++counter as opposed to counter++. Is this really any more efficient (as I have been led to believe elsewhere) because there is no assignment being done? Thanks in advance Rich

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  • Which method of adding items to the ASP.NET Dictionary class is more efficient?

    - by ahmd0
    I'm converting a comma separated list of strings into a dictionary using C# in ASP.NET (by omitting any duplicates): string str = "1,2, 4, 2, 4, item 3,item2, item 3"; //Just a random string for the sake of this example and I was wondering which method is more efficient? 1 - Using try/catch block: Dictionary<string, string> dic = new Dictionary<string, string>(); string[] strs = str.Split(','); foreach (string s in strs) { if (!string.IsNullOrWhiteSpace(s)) { try { string s2 = s.Trim(); dic.Add(s2, s2); } catch { } } } 2 - Or using ContainsKey() method: string[] strs = str.Split(','); foreach (string s in strs) { if (!string.IsNullOrWhiteSpace(s)) { string s2 = s.Trim(); if (!dic.ContainsKey(s2)) dic.Add(s2, s2); } }

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  • If there is a necessary data base

    - by Dmitry
    Hello! I have a desktop program which uses an embedded data base mechanism. For the first time a user will execute a program, it must create a database. So that, next time there is a data base and there is no need to create it. Please, tell me, how to chech if there is a necessary data base.

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  • What would be a better way of doing the following

    - by thecoshman
    if(get_magic_quotes_gpc()) { $location_name = trim(mysql_real_escape_string(trim(stripslashes($_GET['location_name'])))); } else { $location_name = trim(mysql_real_escape_string(trim($_GET['location_name']))); } That's the code I have so far. seems to me this code is fundamentally ... OK. Do you think I can safely remove the inner trim(). Please try not a spam me with endless version of this, I want to try to learn how to do this better.

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  • ASP.NET problem - Firebug shows odd behaviour

    - by Brandi
    I have an ASP.NET application that does a large database read. It loads up a gridview inside an update panel. In VS2008, just running on my local machine, it runs fantastically. In production (identical code, just published and put on one of our network servers), it runs slow as dirt. Debug is set to false, so this is not the cause of the slow down. I'm not an experienced web developer, so besides that, feel free to suggest the obvious. I have been using Firebug to determine what's going on, and here is what that has turned up: On production, there are around 500 requests. The timeline bar is very short. The size column varies from run to run, but is always the same for the duration of the run. Locally, there are about 30 requests. The timeline bar takes up the entire space. Can anyone shed some light on why this is happening and what I can do to fix it? Also, I can't find much of anything on the web about this, so any references are helpful too.

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  • MVC way of handling data input

    - by korki
    I have a data input module where I add the information of my product and its sub information like: product basic info product price info product price details price info and price details are related to product and are lists In my web forms approach I would store my main product object on the view state and I would populate it's pricing info and details while doing ajax postbacks. This way I can create a compact module that is very user friendly in terms of defining a lot of data from one place without the need to enter these data from seperate modules. And when I am done I would do one product.save() and that would persist all the data to the respective tables on db. Now I am building similar app on .net mvc framework and pondering on what would be the good way of handling this on mvc. I don't resonate towards storing all this on client side till I click save. And saving to the db after each action makes me remember the days I was coding on asp. Will appreciate your inputs on ways to approach this on mvc framework

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  • Problem mapping data located in a NSMutableArray

    - by Graeme
    I have an NSMutableArray which contains some addresses which I need to map using Apple's MapKit SDK which I can't seem to get to load. The NSLog keeps telling me that the data source is (null) and a 0x0 error displays when I attempt to print out the array. Any ideas? The data is parsed and stored from another class, perhaps I'm not linking it across properly? The data is originally gathered from an RSS feed, bought into the app with an IMporter class, and then displayed in a table view. I want to be able to connect into that data with my mapping class, but am struggling to do so.

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  • Optimizing NSNumber numberWithInt:

    - by Riviera
    I am profiling an iPhone app and I noticed a strange pattern. In a certain block of code that's called quite frequently... [item setQuadrant:[NSNumber numberWithInt:a]]; [item setIndex:[NSNumber numberWithInt:b]]; [item setTimestamp:[NSNumber numberWithInt:c]]; [item setState:[NSNumber numberWithInt:d]]; [item setCompletionPercentage:[NSNumber numberWithInt:e]]; [item setId_:[NSNumber numberWithInt:f]]; ...the first call to [NSNumber numberWithInt:] takes an inordinate amount of time, in the order of 10-15x that of the remaining calls. I've verified that the results are consistent if I shuffle the lines (the first line is always the slow one, by the same ratio). Is there something going on that I'm not aware of? Perhaps this happens because this block is inside a try/catch?

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  • Sync data between a windows desktop app and windows mobile client app

    - by Chris W
    I need to knock up a very quick prototype/proof of concept application to demo to someone within the next couple of days so I've minimal time to research this as fully as I normally would. The set-up is a very simple database application running on a laptop - will only ever be a single user updating a couple of tables so I was thinking of knocking up a basic Win Forms app against SQL Compact. Visual Studio's auto generated data grid edit screens will be fine with a little customisation. The second aspect is to then add a windows mobile client application that can pull data from both tables stored on the laptop, edit some data and insert some extra rows before sending the changes back to the laptop copy of the database. I've not done any WinMo development so what's the best approach for me to look at. Is it easy enough to sync data between the two databases when the WinMo device is connected to the laptop with USB? Most of the samples I've looked at so far seem to be syncing SQL Compact with SQL Standard using IIS which seems a bit overkill. The volumes of data to be synced are so small that I can easily write some manual sync code if it's easy for me to query/update the Compact DB from the laptop application when the device is connected.

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  • Extracting Data Daily from MySQL to a Local MySQL DB

    - by Sunny Juneja
    I'm doing some experiments locally that require some data from a production MySQL DB that I only have read access to. The schemas are nearly identical with the exception of the omission of one column. My goal is to write a script that I can run everyday that extracts the previous day's data and imports it into my local table. The part that I'm most confused about is how to download the data. I've seen names like mysqldump be tossed around but that seems a way to replicate the entire database. I would love to avoid using php seeing as I have no experience with it. I've been creating CSVs but I'm worried about having the data integrity (what if there is a comma in a field or a \n) as well as the size of the CSV (there are several hundred thousand rows per day).

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  • How to find root cause for "too many connections" error in MySQL/PHP

    - by Nir
    I'm running a web service which runs algorithms that serve millions of calls daily and run some background processing as well. Every now and than I see "Too many connections" error in attempts to connect to the MySQL box" for a few seconds. However this is not necessarily attributed to high traffic times or anything I can put my finger on. I want to find the bottleneck causing it. Other than in the specific times this happens the server isn't too loaded in terms of CPU and Memory, and has 2-3 connections (threads) open and everything works smoothly. (I use Zabbix for monitoring) Any creative ideas on how to trace it?

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  • mysql: inserting data and autoincrement

    - by every_answer_gets_a_point
    i am converting from access to mysql i have a table in access where one of the columns is an autonumber when i transfer the data into the mysql database (where i also have a column that is auto_increment), should i be transfering the auto_increment data into the auto_increment column, or will it auto_increment itself? how do i ensure that if i do not transfer the autoincrement data from access, that it auto_increments properly?

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  • Reading data from a COM port

    - by Demonick
    I want to get input from a barcode-scanner, which is connected to a CHD cash register, which is connected to a Windows XP PC trough a COM port. I want to read the data from the scanner and the cash register, and send the data to a program, which has a table with items in a shop. And provide a function which removes items, too. Where should I start? Is there a code in Delphi or Java, that can get that data into a program?

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  • Faster code with another compiler

    - by Andrei
    I'm using the standard gcc compiler in math software development with C-language. I don't know that much about compilers or compiler options, and I was just wondering, is it possible to make faster executables using another compiler or choosing better options? The default Makefile sets options -ffast-math and -O3 and I think both of them have some impact in the overall calculation time. My software is using memory quite extensively, so I imagine some options related to memory management might do the trick? Any ideas?

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  • What are the suggested alternatives for Class<T>.isAssignableFrom(Class<?> cls)?

    - by Wing C. Chen
    Currently I am doing the profiling to a piece of code. During the profiling, I discovered that this very method call, Class<T>.isAssignableFrom(Class<?> cls) takes up to quite amount of the entire time. Because this is a method from reflection, it takes a lot of time compared to normal keywords or method calls. I am wondering if there are some good alternatives for this method calls?

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  • move data from one table to another, postgresql edition

    - by IggShaman
    Hi All, I'd like to move some data from one table to another (with a possibly different schema). Straightforward solution that comes into mind is - start a transaction with serializable isolation level; INSERT INTO dest_table SELECT data FROM orig_table,other-tables WHERE <condition>; DELETE FROM orig_table USING other-tables WHERE <condition>; COMMIT; Now what if the amount of data is rather big, and the <condition> is expensive to compute? In PostgreSQL, a RULE or a stored procedure can be used to delete data on the fly, evaluating condition only once. Which solution is better? Are there other options?

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  • change data frame columns to rows

    - by Sol Lago
    Sorry if this is obvious: I found a lot of questions similar to mine but I can't figure it out for my own data. I have a data frame that looks like this: A <- c(1,6) B <- c(2,7) C <- c(3,8) D <- c(4,9) E <- c(5,0) df <- data.frame(A,B,C,D,E) df A B C D E 1 1 2 3 4 5 2 6 7 8 9 0 And I need this: df X1 A 1 A 6 B 2 B 7 C 3 C 8 D 4 D 9 E 5 E 0 Thanks!

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