duplicates

问题 I'm considering an optimisation in a particularly heavy part of my code. It's task is to insert statistical data into a table. This data is being hit a fair amount by other programs. Otherwise I would consider using SQL Bulk inserts etc. So my question is... Is it ok to try and insert some data knowing that it might (not too often) throw a SqlException for a duplicate row? Is the performance hit of an exception worse than checking each row prior to insertion? 回答1: First, my advice is to err

问题 Can anybody tell me why this doesn't work as expected? <?php $merchant_string = '123-Reg|Woolovers|Roxio|Roxio|BandQ|Roxio|Roxio|Big Bathroom Shop|Roxio|Robert Dyas|Roxio|Roxio|PriceMinister UK|Cheap Suites|Kaspersky|Argos|Argos|SuperFit|PriceMinister UK|Roxio|123-Reg'; $merchant_array = explode('|', $merchant_string); for($i = 0; $i<count($merchant_array); $i++) { $merchant_array = array_unique($merchant_array); echo $merchant_array[$i] . '<br />'; } ?> The results I get is: Woolovers Roxio

问题 I made a mistake in a bulk insert script, so now i have "duplicate" rows with different colX. I need to delete this duplicate rows, but I cant figure out how. To be more precise, I have this: col1 | col2 | col3 | colX ----+---------------------- 0 | 1 | 2 | a 0 | 1 | 2 | b 0 | 1 | 2 | c 0 | 1 | 2 | a 3 | 4 | 5 | x 3 | 4 | 5 | y 3 | 4 | 5 | x 3 | 4 | 5 | z and I want to keep the first occurrence of each (row, colX): col1 | col2 | col3 | colX ----+---------------------- 0 | 1 | 2 | a 3 | 4 | 5

问题 I have the following JS array: var myArray = [{name:"Bob",b:"text2",c:true}, {name:"Tom",b:"text2",c:true}, {name:"Adam",b:"text2",c:true}, {name:"Tom",b:"text2",c:true}, {name:"Bob",b:"text2",c:true} ]; I want to eliminate the indexes with name value duplicates and recreate a new array, with distinct names, eg: var mySubArray = [{name:"Bob",b:"text2",c:true}, {name:"Tom",b:"text2",c:true}, {name:"Adam",b:"text2",c:true}, ]; As you can see, I removed "Bob" and "Tom", leaving only 3 distinct

问题 just wondering why duplicated behaves the way it does with NAs: > duplicated(c(NA,NA,NA,1,2,2)) [1] FALSE TRUE TRUE FALSE FALSE TRUE where in fact > NA == NA [1] NA is there a way to achieve that duplicated marks NAs as false, like this? > duplicated(c(NA,NA,NA,1,2,2)) [1] FALSE FALSE FALSE FALSE FALSE TRUE 回答1: You use the argument incomparables for the function duplicated like this : > duplicated(c(NA,NA,NA,1,2,2)) [1] FALSE TRUE TRUE FALSE FALSE TRUE > duplicated(c(NA,NA,NA,1,2,2)

问题 I have a data.table that looks like this dt <- data.table(ID=c("A","A","B","B"),Amount1=c(100,200,300,400), Amount2=c(1500,1500,2400,2400),Dupl=c(1,0,1,0)) ID Amount1 Amount2 Dupl 1: A 100 1500 1 2: A 200 1500 0 3: B 300 2400 1 4: B 400 2400 0 I need to duplicate each row that has a 1 in the Dupl column and replace the Amount1 value with the Amount2 value in that duplicated row. Besides that I need to give that duplicated row the value 2 in Dupl. This means it should look like this: ID

问题 I expect I'll be able to make a work around but I can't for the life of me understand why this code is not functioning correctly and allowing duplicate entries to be added to the List. The if statement condition is never met, even when I drag identical files in from the same location. I don't understand why the "Contains" method isn't matching them up. public class Form1:Form { private List<FileInfo> dragDropFiles = new List<FileInfo>(); private void Form1_DragDrop(object sender,

问题 In my MatchCollection, I get matches of the same thing. Like this: string text = @"match match match"; Regex R = new Regex("match"); MatchCollection M = R.Matches(text); How does one remove duplicate matches and is it the fastest way possible? Assume "duplicate" here means that the match contains the exact same string. 回答1: Linq If you are using .Net 3.5 or greater such as 4.7, linq can be used to remove the duplicates of the match. string data = "abc match match abc"; Console.WriteLine

问题 In my MatchCollection, I get matches of the same thing. Like this: string text = @"match match match"; Regex R = new Regex("match"); MatchCollection M = R.Matches(text); How does one remove duplicate matches and is it the fastest way possible? Assume "duplicate" here means that the match contains the exact same string. 回答1: Linq If you are using .Net 3.5 or greater such as 4.7, linq can be used to remove the duplicates of the match. string data = "abc match match abc"; Console.WriteLine

问题 This question already has answers here : Java Random number with no duplicate [duplicate] (5 answers) Closed last year . For my computer science class we're supposed to redo a lottery code we have already created, but now using methods and arrays. This is what I've done so far, but I can't figure out for the life of me why it is still duplicating the numbers and I can't find anything online that is close enough to what we're supposed to be doing/topics we have gone over. I am very new to this