Listado de la etiqueta: Duplicates


“Have you ever heard about the data duplication concept while working in databases? When a record, thing, person, or place has its exact copy, that copy is said to be the duplicate of the flamante. While working in traditional databases, we use the WHERE clause to find out the duplicates within the table records, i.e., SQL, PostgreSQL. On the other hand, MongoDB doesn’t allow you to use the WHERE clause to find out the duplicates inserted within the collections of a specific database.

It came up with the aggregate function to find out the duplicate values from the collection. Within this article today, we will be discussing the insertion of duplicate records within the Mongo DB collections and display them on the MongoDB shell using the aggregate command of collections. Let’s start with our today’s article by the use of apt update and upgrade instructions within the terminal shell of the Ubuntu 20.04 system. For that, you need to log in first and open the shell by the use of “Ctrl+Alt+T.” After that, you can try the shown-below instruction at your shell and add the password for the user to continue the update process.”

It might require your confirmation to continue this process. Tap “y” upon asking: “Do you want to continue?”. After that, hit the Enter key.

It may take more or less time to process according to the situation of your system.

After the complete update, you will get the shown-below last lines of processing.

After the successful system update and upgrade, we have to open the MongoDB shell to insert some collections and records within the database. So, we have been using the “mongo” query to do so, as displayed in the image. The shell has been prepared successfully.

While using the “db” instruction at the MongoDB shell, we have found that the “test” database is available for our use.

Therefore, we have been using the “test” database for further queries and creating collection within it. For that, try the “use” instruction followed by the name of a database, i.e., “test.”

To add records, we need a collection in the test database. Thus, we need to create a new collection. For that, we have to try out the “db” instruction along with the “createCollection()” function of MongoDB, followed by the name of a new collection within its parenthesis, i.e., Data. The query was successful, and the collection was created successfully as per the status “ok: 1”. Moreover MongoDB, we tend to utilize the find() function preceded by the collection name to display the records of a specific collection. Therefore, we have tried the “db” instruction followed by the collection name, i.e., Data, and the function find() to do so. The collection “Data” is empty right now. Thus, we need to add some records to the collection.

To insert the records within the Data collection of MongoDB, we need to try out the insert() function within the “db” instruction along with the data in the form of documents, i.e., list format. We have been using a total of 4 columns for the document data of collections, i.e., _id, title, age, and price. We have added a total of 5 records for all these 4 columns of Data collection.

The record was added successfully as per the output above shows the number of records 5 for the “nInserted” option. After this, we will be using the find() function with the “Data” collection to find and display all the records of this collection. We are not passing any arguments to the parenthesis of a find() function to not restrict the collection records. All the 5 records for Data collection have been presented in the Mongo DB shell.

As we have been dealing with the topic of finding the duplicates in the collections of MongoDB, we must have some duplicate records in the collections as well. Therefore, we have been inserting three more records within the Data collection to be used as duplicates of some of the already inserted records. We need to update the “_id” column only as the ID of any column must be unique in MongoDB as we used to do in traditional databases. The same insert function has been used so far with the “Data” collection name. All three records have been added.

Now, when you run the “db” instruction with the collection name “Data” followed by the find() function merienda again on the MongoDB shell, the total of 8 records will be displayed on your screen. We can see the duplicate values for columns other than “_id” in this collection data.

It’s time to try out the aggregate() method for the “Data” collection to list out the specific column values that are duplicated in it. You need to use the shown-below syntax of an aggregate command in MongoDB. The option “$group” is used to add all duplicate values of a specific column in one, while the option $match will be utilized to find out the groups having more than 1 document. On the other hand, the “$project” option will be used to specify the format of showing the duplicate records. The first field of the “$group” option will specify the column name in which we will be searching for duplicates. A total of 3 records have been found duplicated for the column “title” of a Data collection. After this, the same query was tried for the “age” column and got the 3 results again.

Conclusion

The explanation of duplicate records has been given in the introductory paragraph, and we have discussed the difference between finding out the duplicates from traditional databases and MongoDB. For this purpose, we have tried to give an illustration about making a new collection within MongoDB and inserting records within it. Moreover, we have discussed the use of the aggregate function to find out the specific column containing the duplicate value within the collections. This article has displayed the clear difference in finding out the duplicates for MongoDB as a comparison to any other database.



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This article will discuss different methods of removing duplicate items from a list in the C# programming language. These methods will be very useful in detecting and removing redundancy when adding and storing data in a list. The use of different C# libraries such as LINQ and collections.generic will also be discussed in this article. The most effective method to remove duplicates is the Distinct() and ToList() method, which eliminates all duplicates in one go and creates a list with unique elements. This method is present in the LINQ library of the C# Programming language.

The Distinct() Method

We use the Distinct() method to distinguish between items or variables. The LINQ library provides the Distinct method, this functionality to compare items or variables in the C# programming language as it is a query-based library. This method only removes duplicates from a single data source and returns the unique items into a new data source that would be a list. In our case, we will be using this method for the List class, so we will also add the ToList() method with the Distinct() method so that when the distinct items are recognized, they can be added to a new list.

The following is the syntax for writing this method in the C# programming language:

# “list name = list.Distinct().ToList();”

As can be seen, the method is used while creating a new list since it returns elements from an existing list to create a unique list. When initializing a list using this method, we must use the old list before calling the method for the inheritance of previous items of the old list.

Now that we know about the syntax, we will implement some examples and test this method with different data types of items in the C# programming language.

Example 01: Using the Distinct().ToList() Method to Remove Numbers From a List in Ubuntu 20.04

In this instance, we will be using the Distinct().ToList() method to remove numbers from an integer list in the C sharp programming language. We will first call the LINQ library, which has the Distinct().ToList() method so that it can be used further in the program. We will be transforming a list with duplicate entries and making a new list with unique values with the help of the distinct method. This method will be performed in the Ubuntu 20.04 environment.

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In the prior C# program, we created an integer data type list and then used the system’s Add() function to add some items to it. We’ll make a new list and apply values to it using the “Distinct().ToList()” function, which will eliminate all of the duplicates. On the output screen, the list with the unique objects will be printed.

After compiling and executing the above program, we will get the following output as shown in this snippet below:

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In the above output, we can see that all the entries of the list that were printed are unique and there are no duplicate items, and we have successfully removed duplicates from the list.

Example 02: Using the Distinct().ToList() Method to Remove Alphanumeric String From a List in Ubuntu 20.04

In this illustration, we will use the “Distinct().ToList()” method to remove duplicates from a string data type list, but the members of the list will be Alphanumeric characters to observe how the “Distinct().ToList()” method adapts. We will use the add function in the system to repeat the process of initializing a list.Library of collections. The function “Distinct().ToList()” creates a new list with unique entries. Due to its distinctiveness, the new list would then be utilized for future preference.

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In the preceding C# code, we created a string data type list and then used the Add() function from the “system.collection” package to add some alphanumeric values to it. We will make a new list and apply values to it with the “Distinct().ToList()” method, which will eliminate all of the duplicates. On the output screen, the list with the unique objects will be printed.

After compiling and running the given C# code, we will get the following result, as seen in the image below:

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We can see that all of the entries in the printed list are unique, and there are no duplicates, indicating that the Distinct function was effective in eliminating duplicates from the list.

After this, we will be looking into some different approaches to remove duplicates from a list in the C# programming language.

Using the Hash Set Class to Remove Duplicates in Ubuntu 20.04

In this method, we will be using the hash set class two to remove duplicates from a list using an object of the class and adding it to a new list. The hash set is a data set that only contains unique items from the “System.Collections.Generic” namespace. We will use the hash set class and create a new list in which there will be no duplicates due to the unique property of the hash set.

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In the above C# program, we have initialized an integer data type list and assigned some numeric values to it. Then we created an object of the hash set class, which we then used in the value assigning of a new list so that it would have distinct values when it is printed using the display list function.

The output after compiling and executing this program is shown below:

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As we can see in the output that the new list we created with the Hash set object has no duplicates as the add shared object successfully removed all the repetitive elements of the old list.

Using the IF Check to Remove Duplicates in Ubuntu 20.04

In this method, we will be using the traditional if check to verify that there are no duplicates present in the list. The if check will add only the unique items from the list and create a completely distinct list with no repetitions. We will use the foreach loop for traversing through the list to check for duplicates, not so for printing the new list with unique elements.

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In the above C# program, we have initialized a string data type list and assigned some text values to it with several duplicate items. Then we started a for each loop in which we nested an if check, and we added all the unique items to a new list that we initialized before starting the for each loop. After this, we started another for each loop in which we printed all the elements of the new list. The result of this C# program will be as shown below on the output screen.

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As we can see in the output screen, all the elements of the new list are unique as compared to the old list, which had several duplicates. The if check eliminated all the duplicates from the old list and added them to the new list that we saw on the output screen.

Conclusion

In this article, we discussed several different approaches to removing duplicate items from the list data type of the C# programming language. The different libraries of the C# language were also used in these approaches as they provided different functions and methodologies to implement this concept. The Distinct method was discussed in great detail as it is a very effective and precise method to remove duplicates from a list in the C# programming language. To eliminate duplicates from the list, we utilized the hash set class and the standard IF check. All these approaches were implemented in the Ubuntu 20.04 environment to understand the different methods better.



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