duplicate-removal

问题 I am using postgres. I want to delete Duplicate rows. The condition is that , 1 copy from the set of duplicate rows would not be deleted. i.e : if there are 5 duplicate records then 4 of them will be deleted. 回答1: Try the steps described in this article: Removing duplicates from a PostgreSQL database. It describes a situation when you have to deal with huge amount of data which isn't possible to group by . A simple solution would be this: DELETE FROM foo WHERE id NOT IN (SELECT min(id) --or

问题 Using LINQ, from a List<int> , how can I retrieve a list that contains entries repeated more than once and their values? 回答1: The easiest way to solve the problem is to group the elements based on their value, and then pick a representative of the group if there are more than one element in the group. In LINQ, this translates to: var query = lst.GroupBy(x => x) .Where(g => g.Count() > 1) .Select(y => y.Key) .ToList(); If you want to know how many times the elements are repeated, you can use:

问题 It's difficult to tell what is being asked here. This question is ambiguous, vague, incomplete, overly broad, or rhetorical and cannot be reasonably answered in its current form. For help clarifying this question so that it can be reopened, visit the help center. Closed 7 years ago . In this question: Detecting duplicate lines on file using c i can detect duplicate lines, but how we can remove this lines from our file? Thanks. Edit : To add my code : #include <stdio.h> #include <stdlib.h>

问题 So yesterday I posted my first SO question, and it went down like a ton of bricks. However I've picked myself up, dusted myself off, and hopefully this question will be more acceptable... :-) I am trying to remove data duplicates from a list of Health Questionnaires I have to monitor, but the tricky bit I was struggling with was finding a duplicate in one column, AND then checking that the data on the same row, for the 3 adjacent columns were also duplicates. Storing the searched for

问题 I have an Sqlite3 database with a table like this: Table(com1, com2) A || B B || A C || D D || B B || D If I have 2 rows: A || B, and B || A, I want to delete one of them (I don't care which one). So to obtain: A || B C || D D || B I've read the many asks about duplicate rows but I cant find something like this. Thanks for any help. 回答1: I think solution for your problem should look like this: SELECT t1.val1,t1.val2 FROM table AS t1 JOIN table AS t2 ON ( (t1.val1=t2.val2) AND (t1.val2=t2.val1

问题 After reading through most of the maps questions, I eventually got an idea from this link: How to unique my data that are stored in an object which are stored in a vector? I have a task of storing X , Y , Z coordinates from the user input. To prevent the user from entering duplicated data, I have decided to use map containers as they do not allow duplicated data. I tested the code out. I am using X as the key and Y as the value I am able to store X and Y via this: map<int, int> mapp2d; mapp2d

问题 I am dynamically generating a query like below that creates different combinations of rules by left joining (any number of times) on itself and avoiding rules with some of the same attributes as part of the joins conditions e.g. SELECT count(*) FROM rules AS t1 LEFT JOIN rules AS t2 ON t1.id != t2.id AND ... LEFT JOIN rules AS t3 ON t1.id != t2.id AND t1.id != t3.id AND t2.id != t3.id AND ... I am currently removing duplicates by creating an array of ids from the joined rows then sorting and

问题 I have a file (size = ~1.9 GB) which contains ~220,000,000 (~220 million) words / strings. They have duplication, almost 1 duplicate word every 100 words. In my second program, I want to read the file. I am successful to read the file by lines using BufferedReader. Now to remove duplicates, we can use Set (and it's implementations), but Set has problems, as described following in 3 different scenarios: With default JVM size, Set can contain up to 0.7-0.8 million words, and then

问题 select * from ap; select name from ap group by name having count(*)>1; I want to delete duplicates records from this table. 回答1: delete from table_name a where a.rowid > any (select b.rowid from table_name b where a.col1 = b.col1 and a.col2 = b.col2); 回答2: If you want to keep one record for each name: delete from ap where ap.id > (select min(ap2.id) from ap ap2 where ap2.name = ap.name) 回答3: 1. solution delete from emp where rowid not in (select max(rowid) from emp group by empno); 2.

问题 I want to create a method to eliminate duplicates from a text file. Edit: Why am i getting downvoted ? It's not like I didn't search through the web before asking. For example, the data in the text file: Fruits:Edible:Inedible Apple:5:10 Apple:1:2 Pear:5:1 Orange:20:1 Pear:5:1 Apple:5:10 Orange:1:20 Orange:20:1 I have a class of apple, orange, pear according to this example. Using the class, I have created 3 different object vector to store them in, using set methods. For example if Apple is