Sql delete duplicates except one

In this article we look at ways to remove all duplicate rows except one in an SQL database. Delete all duplicates rows except one in SQL Server Recently, I got one request for one script to delete duplicate records in PostgreSQL. Most of the Database Developers have such a requirement to delete duplicate records from the Database. I have a table that contains duplicate rows. Using grouping I can easily identify those rows.

As of now, I count the grouped records and copy one of the group in a temporary table together with its count of elements. Than I loop over this table and delete N - rows of each group from the original table. Unfortunately this is done with two cursors and WHILE loops. Then delete each row except the first one returne for each set of duplicates.

DELETE nFROM names n names nWHERE n1. I used this method in MySQL 5. Not sure about other versions. T-SQL: Deleting all duplicate rows. Use any one of above methods to delete duplicate rows.

Good to know about other scenarios of deleting duplicates : If you want to delete duplicates of a particular ID(here empid) then use Delete Top( ) clause as shown below. An explanation of how to find rows with duplicate values in a table using SQL. Finishes by showing how to stop people entering new duplicates ! Delete all Duplicate Rows except for One record in MySQL NB – You need to do this first on a test copy of your table! When I did it, I found that unless I also included AND n1. In this post Find and Delete all duplicate rows but keep one , we are going to discuss that how we can find and delete all the duplicate rows of a table except one row.

Assume that we have a table named tbl_sample which has four columns - EmpI EmpName, Age, and City. In the end this query allows us to remove duplicate records, but to keep all information from the first of each of the duplicate records, exactly what we want! Below is a full working example of the process in action. Essentially, it deletes all the duplicates except for the one with the highest value for the primary key. If a table has a unique column such as a number or integer, that will reliably return just one value with MAX() or MIN(), then you can use this technique to identify the chosen survivor of the group of duplicates.

How do I delete all-but-one of duplicate query-matching records in a single Access table? Same question for an SQL table. Hi All,I need to delete duplicate records from one table with keeping one copy of original. SQL Server supports EXCEPT clause which returns all records present in the first table and absent in the second one.

But this clause eliminates duplicates and cannot be used as a subject to a DML operation. ANSI SQL standard describes EXCEPT ALL which returns all records from the first table which are not present in the second table, leaving the duplicates as is. The query delete from CTE_ Duplicates where rownumber! B) Delete duplicate rows using an intermediate table. The following shows the steps for removing duplicate rows using an intermediate table: Create a new table with the structure the same as the original table that you want to delete duplicate rows.

Insert distinct rows from the original table to the immediate table.