How do I find duplicate values in a table in Oracle?

sql oracle duplicate-data
Andrew picture Andrew · Sep 12, 2008 · Viewed 728.2k times · Source

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

Bill the Lizard picture Bill the Lizard · Sep 12, 2008

Aggregate the column by COUNT, then use a HAVING clause to find values that appear greater than one time.

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

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