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

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_nameGROUP BY column_nameHAVING COUNT(column_name) > 1;

sql oracle duplicate-data

Another way:

SELECT *FROM TABLE AWHERE EXISTS (  SELECT 1 FROM TABLE  WHERE COLUMN_NAME = A.COLUMN_NAME  AND ROWID < A.ROWID)

Works fine (quick enough) when there is index on column_name. And it's better way to delete or update duplicate rows.

sql oracle duplicate-data

Simplest I can think of:

select job_number, count(*)from jobsgroup by job_numberhaving count(*) > 1;

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