![]() We can also delete duplicate records by using the “Rank()” function. The above query deletes all duplicate records with “” greater than 1. If we want to delete duplicate records using CTE, then we have to add a “Where” clause with the condition “ > 1”. The above query “” column gives a unique row id for each duplicate row. WITH CTE(,, )ĪS (SELECT, , ROW_NUMBER() OVER(PARTITION BY, ORDER BY ) AS CTE is available in SQL Server 2005 or higher version. We use the “Row_Number” function and Common Table Expressions to find duplicate values. GROUP BY, ) By Using Common Table Expressions (CTE) To delete the duplicate records, we can use the below query. In the above query, we will exclude the minimum id of each duplicate row. We can use the “MIN” function to get the first record of all duplicate records. Now we need to keep one record and delete all duplicate records. In the above query, we will get all data having duplicated more than one, and the “” column shows how many duplicate records there are. We can use the COUNT function.įor example, SELECT, , = COUNT(*) VALUES('Malaya Kabiraj', 'Kolkata') By Using Group By and Having a clauseīy using Group By clause, we can group all table data as per our defined columns and count the duplicate occurrence of rows. ![]() In this article, we will find duplicate values using the "Group By and Having" clause, "Common Table Expressions (CTE)," and "Rank" function.įor this operation, we will create a table named “employee” and add some records. Now you should know how to delete duplicate records in the Oracle Database.This article will teach us how to find and delete duplicate values from a SQL server table. Sometimes we may find duplicate values in a table, and we have to find the duplicate values from that table. The following query verifies the delete operation: SELECTįruits Code language: SQL (Structured Query Language) ( sql ) ) Code language: SQL (Structured Query Language) ( sql ) Because the rowid is unique to each row, you can use it to remove the duplicates as shown below: DELETE FROM In this case, you can use the rowid which is a physical locator that specifies where on storage Oracle stores the row. In the fruits table, the values in all columns fruit_id, fruit_name, and color have copies. INSERT INTO fruits(fruit_id,fruit_name,color) VALUES( '4,Banana', 'Green') INSERT INTO fruits(fruit_id,fruit_name,color) VALUES( 3, 'Banana', 'Yellow') INSERT INTO fruits(fruit_id,fruit_name,color) VALUES( 2, 'Orange', 'Orange') INSERT INTO fruits(fruit_id,fruit_name,color) VALUES( 1, 'Apple', 'Red') Let’s drop and create the fruits table with a new structure and data as follows: DROP TABLE fruits If all values in all columns can have copies, then you cannot use the fruit_id column anymore. This method above works if you have a column that is not part of the group for evaluating duplicates. Likewise, if you want to keep the row with the lowest ID, you use the MIN() function instead of the MAX() function: DELETE FROM Three rows were deleted which is what we expected: SELECT You use the following DELETE statement with a subquery to delete rows whose values are in the fruit_id column are not the highest ones. The following query returns the last entry for each combination of fruit_name and color: SELECT MAX(fruit_id) ![]() Suppose you want to keep the row with the highest fruit_id and delete all other copies. query data from the fruit table SELECT * FROM fruits Ĭode language: SQL (Structured Query Language) ( sql ) INSERT INTO fruits(fruit_name,color) VALUES( 'Banana', 'Green') ![]() INSERT INTO fruits(fruit_name,color) VALUES( 'Banana', 'Yellow') INSERT INTO fruits(fruit_name,color) VALUES( 'Orange', 'Orange') INSERT INTO fruits(fruit_name,color) VALUES( 'Apple', 'Red') insert sample rows INSERT INTO fruits(fruit_name,color) VALUES( 'Apple', 'Red') In this case, you need a column in the table like id column that is not the part of the group used to evaluate duplicate.Ĭonsider the following fruits table: - create fruit table CREATE TABLE fruits (įruit_id NUMBER generated BY DEFAULT AS IDENTITY, For example, you may want to preserve the newest or oldest row. It is better to construct a single statement that removes all unwanted copies in one go.īefore removing the duplicate records, you must decide which instances you want to keep. However, it is time-consuming to do it manually if the table has a large number of duplicate records. If a table has a few duplicate rows, you could do this manually one by one by using a simple DELETE statement. Once you’ve found the duplicate records in a table, you often want to delete the unwanted copies to keep your data clean. Summary: in this tutorial, you will learn step by step how to delete duplicate records in Oracle Database using the DELETE statement with a subquery. ![]()
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