Question

What’s the simplest SQL statement that will return the duplicate values for a given column and the count of their occurrences in an Oracle database table?

For example: I have a JOBS table with the column JOB_NUMBER. How can I find out if I have any duplicate JOB_NUMBERs, and how many times they’re duplicated?

Answer 1

Aggregate the column by COUNT, then use a HAVING clause to find values that appear more than once.

SELECT column_name, COUNT(column_name) FROM table_name GROUP BY column_name HAVING COUNT(column_name) > 1;