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  • Rails/mysql SUM distinct records - optimization

    - by pepernik
    Hey. How would you optimize this SQL SELECT SUM(tmp.cost) FROM ( SELECT DISTINCT clients.id as client, countries.credits_cost AS cost FROM countries INNER JOIN clients ON clients.country_id = countries.id INNER JOIN clients_groups ON clients_groups.client_id=clients.id WHERE clients_groups.group_id IN (1,2,3,4,5,6,7,8,9) GROUP BY clients.id ) AS tmp; I'm using this example as part of my Ruby on Rails project. Note that my nested SQL (tmp) can have more then 10 milion records. You can split that in more SQLs if the performance is better. Should I add any indexes to make it quicker (i have it on IDs)?

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  • Randomize numbers within a subset

    - by Samuel
    I have a array of integer numbers (say 1,2,3,4,5 or 1,2,3, ... 10 or 1,2,3, ... 50) from which I would like to get a random set of numbers ordered differently every time. Is there a utility method to do this? e.g. for 1,2,3,4,5 post randomization it might be either [1,5,4,2,3 or 2,1,3,5,4 or 3,1,2,4,5 or ...] I would like to know if there is a java utility method / class which already provides this capability?

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  • Subset and lagging list data structure R

    - by user1234440
    I have a list that is indexed like the following: >list.stuff [[1]] [[1]]$vector ... [[1]]$matrix .... [[1]]$vector [[2]] null [[3]] [[3]]$vector ... [[3]]$matrix .... [[3]]$vector . . . Each segment in the list is indexed according to another vector of indexes: >index.list 1, 3, 5, 10, 15 In list.stuff, only at each of the indexes 1,3,5,10,15 will there be 2 vectors and one matrix; everything else will be null like [[2]]. What I want to do is to lag like the lag.xts function so that whatever is stored in [[1]] will be pushed to [[3]] and the last one drops off. This also requires subsetting the list, if its possible. I was wondering if there exists some functions that handle list manipulation. My thinking is that for xts, a time series can be extracted based on an index you supply: xts.object[index,] #returns the rows 1,3,5,10,15 From here I can lag it with: lag.xts(xts.object[index,]) Any help would be appreciated thanks: EDIT: Here is a reproducible example: list.stuff<-list() vec<-c(1,2,3,4,5,6,7,8,9) vec2<-c(1,2,3,4,5,6,7,8,9) mat<-matrix(c(1,2,3,4,5,6,7,8),4,2) list.vec.mat<-list(vec=vec,mat=mat,vec2=vec2) ind<-c(2,4,6,8,10) for(i in ind){ list.stuff[[i]]<-list.vec.mat }

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  • Reading a subset of the lines in a text file, with bash

    - by Markus
    Hi! I have a file line a - this is line a line b - this is line b line c - this is line c line d - this is line d line e - this is line e The question is: How can I output the lines starting from "line b" till "line d" using bash commands? I mean, to obtain: "line b - this is line b line c - this is line c line d - this is line d"

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  • MDX filter members in a sum-function

    - by Radagast2005
    I have an SSAS cube containing customers and their purchased memberships (let's say magazines). I want to calculate the retention. I.e. how many customers remain a customer. To do this I specify a set (males, 30yrs, 1 january 2011). I want to see if this set - identified by a customer number - is still present in the following months. I named my set MySet2. What I try to do is: sum(measures.amount, [membership].[name].&[X], MySet2, [date].[date].currentmember) However, the result is incorrect. The number is far to low. I suspect it still tries to account for all the males of 30 years old, but after a year they're not 30 anymore. What am I missing? I looked at scope and filter, but I'm not sure how to apply it.

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  • typeahead.js remote with subset matching

    - by rebelde
    Instead of returning to the server after each additional letter is typed, I want it to only go to the server once, get all matching words, and filter the downloaded data after that. We are having trouble making this work. We are successfully using "remote" to wait until two letters are typed, but we can't get it to stop going to the server as additional letters are typed. Steps: 1. After two letters are typed, retrieve all matching words that start with those two letters. 2. When a third and additional letters are typed, don't go to the server again, just filter from the previous list that was sent. An example: "mo" is typed in. All 100 words that start with "mo" are returned. (Only 10 are shown.) "mor" - now with a third letter, we don't go back to the server. We just find the 20 words that match from within the previous set of words. Can anybody make this work? In real life (using YUI2), we do this and then go back to the server if somebody types in a space after the word. At that point, we know to retrieve additional words. Thanks!

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  • tsql sum data and include default values for missing data

    - by markpirvine
    Hi, I would like a query that will shouw a sum of columns with a default value for missing data. For example assume I have a table as follows: type_lookup: id name 1 self 2 manager 3 peer And a table as follows data: id type_lookup_id value 1 1 1 2 1 4 3 2 9 4 2 1 5 2 9 6 1 5 7 2 6 8 1 2 9 1 1 After running a query I would like a result set as follows: type_lookup_id value 1 13 2 25 3 0 I would like all rows in type_lookup table to be included in the result set - even if they don't appear in the data table. Any help would be greatly appreciated, Mark

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  • Merging tables in MySQL - sum up columns

    - by Alan Williamson
    I have an interesting problem, that i am sure has a simple answer, but i can't seem to find it in the docs. I have two separate database tables, on different servers. They are both identical table schema with the same primary keys. I want to merge the tables together on one server. But, if the row on Server1.Table1 exists in Server2.Table2 then sum up the totals in the columns i specify. Table1{ column_pk, counter }; "test1", 3 "test2", 4 Table2{ column_pk, counter }; "test1", 5 "test2", 6 So after i merge i want: "test1",8 "test2",10 Basically i need to do a mysqldump but instead of it kicking out raw INSERT statements, i need to do a INSERT..ON DUPLICATE KEY UPDATE statements. What are my options? Appreciate any input, thank you

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  • Detecting coincident subset of two coincident line segments

    - by Jared Updike
    This question is related to: How do I determine the intersection point of two lines in GDI+? (great explanation of algebra but no code) How do you detect where two line segments intersect? (accepted answer doesn't actually work) But note that an interesting sub-problem is completely glossed over in most solutions which just return null for the coincident case even though there are three sub-cases: coincident but do not overlap touching just points and coincident overlap/coincident line sub-segment For example we could design a C# function like this: public static PointF[] Intersection(PointF a1, PointF a2, PointF b1, PointF b2) where (a1,a2) is one line segment and (b1,b2) is another. This function would need to cover all the weird cases that most implementations or explanations gloss over. In order to account for the weirdness of coincident lines, the function could return an array of PointF's: zero result points (or null) if the lines are parallel or do not intersect (infinite lines intersect but line segments are disjoint, or lines are parallel) one result point (containing the intersection location) if they do intersect or if they are coincident at one point two result points (for the overlapping part of the line segments) if the two lines are coincident

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  • Sum two rows in one - My Sql

    - by user303832
    I have found some similar posts, but I didn't find them useful. But I didn't know how to group them. I would like to Sum 'No' and 'Not Set' to one row, and to lose 'Not Set' row. So : 'No' = 'No' + 'Not Set' I have something like this : TEST TestCount Month 'Yes' 123 March 'No' 432 March 'Not Set' 645 March 'Yes' 13 April 'No' 42 April 'Not Set' 45 April 'Yes' 133 May 'No' 41 May 'Not Set' 35 May .... And I would like something like this : TEST TestCount Month 'Yes' 423 March 'No' 410 March 'Yes' 154 April 'No' 192 April 'Yes' 130 May 'No' 149 May .... Can anybody help me with this, tnx in advance

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  • What's the best way to return a subset of a list

    - by Pikrass
    I have a list of tasks. A task is defined by a name, a due date and a duration. My TaskManager class handles a std::list<Task> sorted by due date. It has to provide a way to get the tasks due for a specific date. How would you implement that ? I think a good way (from API point of view) would be to provide a std::list<Task>::iterator pair. So I would have a TaskManager::begin(date) method. Do you think this method should get the iterator by iterating from the start of the list until it finds the first task due on that date, or by getting it from a std::map<date, std::list<Task>::iterator> (but then we have to keep it up-to-date when adding or removing tasks) ? And then, how could I implement the TaskManager::end(date) method ?

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  • How to select a subset of results from a select statement

    - by Ankur
    I have a table that stores RDF triples: triples(triple_id, sub_id, pre_id, obj_id) The method (I need to write) will receive an array of numbers which correspond to pre_id values. I want to select all sub_id values that have a corresponding pre_id for all the pre_ids in the array that is passed in. E.g. if I had a single pre_id values passed in... lets call the value passed in preId, I would do: select sub_id from triples where pre_id=preId; However since I have mutliple pre_id values I want to keep iterating through the pre_id values and only keep the sub_id values corresponding to the "triples" records that have both. E.g. image there are five records: triples(1, 34,65,23) triples(2, 31,35,28) triples(3, 32,32,19) triples(4, 12,65,28) triples(5, 76,32,34) If I pass in an array of pre_id values [65,32] then I want to select the first, third, fourth and fifth records. What would I do for that?

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  • Query - Trying to SUM one field based on content of another field

    - by ShaneL
    Table: DayOfWeek Enrollments Monday 35 Monday 12 Saturday 25 Tuesday 15 Monday 9 Tuesday 15 Basically I'm trying to sum the total enrolments for each day. so the Output will look like: DayOfWeek Enrollments Monday 56 Saturday 25 Tuesday 30 I've spent around 4 hours trying to work this out trying many many different ways but no luck. The problem I'm having is i can count how many enrollments for each day but can't have it aligned with the correct day when i run the query e.g. I want The total to be on the same line as the day it was calculated from. (I hope that is clear enough)

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  • "for" loop from program 7.6 from Kochan's "Programming in Objective-C"

    - by Mr_Vlasov
    "The sigma notation is shorthand for a summation. Its use here means to add the values of 1/2^i, where i varies from 1 to n. That is, add 1/2 + 1/4 + 1/8 .... If you make the value of n large enough, the sum of this series should approach 1. Let’s experiment with different values for n to see how close we get." #import "Fraction.h" int main (int argc, char *argv[]) { NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init]; Fraction *aFraction = [[Fraction alloc] init]; Fraction *sum = [[Fraction alloc] init], *sum2; int i, n, pow2; [sum setTo: 0 over: 1]; // set 1st fraction to 0 NSLog (@"Enter your value for n:"); scanf ("%i", &n); pow2 = 2; for (i = 1; i <= n; ++i) { [aFraction setTo: 1 over: pow2]; sum2 = [sum add: aFraction]; [sum release]; // release previous sum sum = sum2; pow2 *= 2; } NSLog (@"After %i iterations, the sum is %g", n, [sum convertToNum]); [aFraction release]; [sum release]; [pool drain]; return 0; } Question: Why do we have to create additional variable sum2 that we are using in the "for" loop? Why do we need "release previous sum" here and then again give it a value that we just released? : sum2 = [sum add: aFraction]; [sum release]; // release previous sum sum = sum2; Is it just for the sake of avoiding memory leakage? (method "add" initializes a variable that is stored in sum2)

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  • Entity Framework: a proxy collection for displaying a subset of data

    - by Jefim
    Imagine I have an entity called Product and a repository for it: public class Product { public int Id { get; set; } public bool IsHidden { get; set; } } public class ProductRepository { public ObservableCollection<Product> AllProducts { get; set; } public ObservableCollection<Product> HiddenProducts { get; set; } } All products contains every single Product in the database, while HiddenProducts must only contain those, whose IsHidden == true. I wrote the type as ObservableCollection<Product>, but it does not have to be that. The goal is to have HiddenProducts collection be like a proxy to AllProducts with filtering capabilities and for it to refresh every time when IsHidden attribute of a Product is changed. Is there a normal way to do this? Or maybe my logic is wrong and this could be done is a better way?

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  • Waiting for a subset of threads in a Java ThreadPool

    - by David Semeria
    Let's say I have a thread pool containing X items, and a given task employs Y of these items (where Y is much smaller than X). I want to wait for all of the threads of a given task (Y items) to finish, not the entire thread pool. If the thread pool's execute() method returned a reference to the employed thread I could simply join() to each of these Y threads, but it doesn't. Does anyone know of an elegant way to accomplish this? Thanks.

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  • Is C really a subset of C++?

    - by Allopen
    What I mean is, can any C code be implemented via C++? Maybe just simply change a compiler? I know C is much more efficient and concise. But despite of these, can C++ used to implement all functions that are implemented by C?

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  • compare two characters based on subset

    - by schultem
    I have a simple dataframe with two columns: df <- data.frame(x = c(1,1,2,2,3), y = c(rep(1:2,2),1), target = c('a','a','a','b','a')) I would like to compare the strings in the target column (find out whether they are equal or not, i.e., TRUE or FALSE) within every level of x (same number for x). First I would like to compare lines 1 and 2, then 3 and 4 ... My problem is that I am missing some comparisons, for example, line 5 has only one case instead of two - so it should turn out to be FALSE. Variable y indicates the first and second case within x. I played around with ddply doing something like: ddply(df, .(x), summarise, ifelse(as.character(df[df$y == '1',]$target), as.character(df[df$y == '2',]$target),0,1)) which is ugly ... and does not work ... Any insights how I could achieve this comparison? Thanks

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  • Fastest possible summing numbers up to N

    - by dada
    Okay so i need really FAST algorithm or code in C if you have any it would be nice. The task is to sum all numbers from 1 to N for a given number N (it can be negative number too), so i did the usual way (you know just summing with loop from 1 to N) but it's not fast enough - i need something faster, i guess that i need the fastest possible way to do this. If anyone could help me, please do. Thanks.

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  • Getting the submatrix with maximum sum?

    - by guirgis
    With the help of the Algorithmist and Larry and a modification of Kadane's Algorithm, here is my solution: int dim = matrix.length; //computing the vertical prefix sum for columns int[][] ps = new int[dim][dim]; for (int i = 0; i < dim; i++) { for (int j = 0; j < dim; j++) { if (j == 0) { ps[j][i] = matrix[j][i]; } else { ps[j][i] = matrix[j][i] + ps[j - 1][i]; } } } int maxSoFar = 0; int min , subMatrix; //iterate over the possible combinations applying Kadane's Alg. //int toplefti =0, topleftj=0, bottomrighti=0, bottomrightj=0; for (int i = 0; i < dim; i++) { for (int j = i; j < dim; j++) { min = 0; subMatrix = 0; for (int k = 0; k < dim; k++) { if (i == 0) { subMatrix += ps[j][k]; } else { subMatrix += ps[j][k] - ps[i-1][k]; } if(subMatrix < min){ min = subMatrix; } if((subMatrix - min) > maxSoFar){ maxSoFar = subMatrix - min; } } } } The only problem left is to determine the submatrix elements, i mean the top left and the bottom right corners. I managed to do this in one dimensional case. Any suggestions?

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