How Can I Efficiently Remove Duplicate Rows in Oracle?

Eliminating Duplicate Rows in Oracle Databases

During database testing, populating tables with sample data often leads to unintentional duplicate entries. This can create problems, especially when trying to establish primary keys.

The Solution: Leveraging ROWID

Oracle's rowid pseudocolumn provides a unique identifier for each row, offering a straightforward solution for removing duplicates. This method ensures data integrity and allows for the proper creation of primary keys.

The following SQL statement efficiently deletes duplicate rows, retaining a single instance from each duplicate set:

<code class="language-sql">DELETE FROM your_table
WHERE rowid NOT IN (
    SELECT MIN(rowid)
    FROM your_table
    GROUP BY column1, column2, column3
);</code>

Remember to replace your_table with your actual table name, and column1, column2, and column3 with the columns that define the unique identifier for your data. For optimal efficiency, consider including all columns in the GROUP BY clause. This query uses rowid to pinpoint and remove duplicates, leaving your data clean and ready for primary key constraints.

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