,S1.ExamDate as S1_ExamDate, S2.ExamDate AS S2_ExamDateįROM. ,S1.Course AS S1_Course, S2.Course as S2_Course as S1_StudentId,S2.StudentId as S2_StudentID Self-Referencing method to finding duplicate students having same name, course, marks, exam date Let us look at the self-referencing method to find duplicates which looks like this: USE UniversityV2 In the self-referencing method, we take two references to the same table and join them using column-by-column mapping with the exception of the ID which is made less than or greater than the other. What if there are thousands of records in this table, then viewing the table won’t be much help. View the Student table to see duplicate records: - View Student table dataįinding Duplicates by Self-referencing Method Let us deliberately insert a duplicate record for Student: Asif to the Student table as follows: - Adding Student Asif duplicate record to the Student table So, we assume that no two students can have the same name, course, marks and exam date. In this case, a table is said to have duplicate records if a student’s Name, Course, Marks, and ExamDate coincide in more than one records even if the Student’s ID is different. Now we are going to introduce duplicate row(s) in the Student table. We are going to discuss now some potential scenarios in which duplicates were introduced and deleted starting from simple to slightly complex situations. You have successfully prepared the sample data by setting up a database with one table and two distinct (different) records. View the table which contains two distinct records at the moment: - View Student table data Let us only add two records to the Student table: - Adding two records to the Student table INT IDENTITY (1, 1) NOT NULL,ĬONSTRAINT PRIMARY KEY CLUSTERED ( ASC) (1) Create UniversityV2 sample database Start by creating a very simple database which consists of only a Student table at the beginning. Preparing Sample Dataīefore we start exploring the different options available to remove duplicates, it is worthwhile at this point to set up a sample database which will help us to understand the situations when duplicate data makes its way into the system and the approaches to be used to eradicate it. This article focuses on a specific scenario, when data inserted into a database table, leads to the introduction of duplicate records and then we will take a closer look at methods for removing duplicates and finally remove the duplicates using these methods. The presence of duplicate rows is a common issue that SQL developers and testers face from time to time, however, these duplicate rows do fall into a number of different categories that we are going to discuss in this article. Once completed, you will be brought back to the Customer page.This article discusses two different approaches available to remove duplicate rows from SQL table(s) which often becomes difficult over time as data grows if this is not done on time. Any store credit, loyalty, and account balances from the duplicates will be transferred to the selected primary profile.ħ. You can choose to keep and do nothing, move the sales history and balances or move sales history, balances, and delete. Under Customer in the modal, select the primary profile you want to merge the duplicates into and choose an action for each duplicate record. Select or search your customer name and the duplicates.ģ. Once selected, click Merge and go to the next group. Any store credit, loyalty, and account balances from the duplicates will be transferred to the selected primary profile.ĥ. The merge modal will appear showing its first group of duplicates found by email.Ĥ. Click the banner to take action and merge your duplicates in bulk.ģ. If your database has customers with duplicate email addresses, a red banner on top of your screen will show. To find and remove duplicate customer records, follow these steps: For bulk mergingĢ. Disclaimer: For merchants using Marsello, other third-party apps, or custom integrations with our Customer API, the merge action will not work.
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