Find out Duplicate Rows in Oracle

Topic Introduction: In this tutorial, we will show how to find out duplicate rows in Oracle.

Method #1

  SELECT LAST_NAME, COUNT (LAST_NAME) "Employee Count"

    FROM employees

GROUP BY LAST_NAME

  HAVING COUNT (LAST_NAME) > 1;

Method #2

SELECT LAST_NAME, rn

  FROM (SELECT LAST_NAME,

               ROW_NUMBER () OVER (PARTITION BY LAST_NAME ORDER BY ROWID) rn

          FROM employees)

 WHERE rn > 1;