How to deal with duplicate data in Oracle database and get only one piece?

In Oracle database, it is a common requirement to deal with duplicate data and keep only one piece. This situation usually occurs when there are duplicate data in the data table, but we only need to keep one of them and remove the remaining duplicate data. Oracle provides some methods to achieve this functionality, including using the ROWID and ROW_NUMBER functions. The following will introduce in detail how to handle duplicate data in Oracle database and only fetch one piece, and provide specific code examples.

Method 1: Using ROWID

In Oracle database, each row of data has a unique ROWID identifier. We can use this feature to remove duplicate data and keep only one. The following is a sample SQL statement:

DELETE FROM your_table
WHERE ROWID NOT IN
(SELECT MIN(ROWID)
FROM your_table
GROUP BY column1, column2, ...);

In the above code, your_table is the data table you want to process, column1, column2, ... is used to Fields to determine duplicate data. These fields are grouped via the GROUP BY clause and the smallest ROWID in each group is selected via the MIN function so that one piece of data is retained and the remaining duplicates are removed.

Method 2: Use the ROW_NUMBER function

Another way to deal with duplicate data is to use the ROW_NUMBER function to number the duplicate data and then delete the data with a number greater than 1. The following is a sample SQL statement:

DELETE FROM
(SELECT column1, column2, ..., ROW_NUMBER() OVER (PARTITION BY column1, column2, ... ORDER BY column1) AS rn
FROM your_table)
WHERE rn > 1;

In the above code, we number the repeated data through the ROW_NUMBER function, while specifying the grouping field through the PARTITION BY clause, and the ORDER BY clause specifying the sorting field. Finally, delete data with a number greater than 1 and retain data with a number of 1.

The above are two common methods of processing duplicate data in Oracle database to only take one. According to the specific situation and needs, choose the appropriate method to handle duplicate data and maintain the uniqueness and integrity of the data.

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