How To Count Duplicated Values in a Column?
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How To Count Duplicated Values in a Column?
by Micheal Sun Jan 17, 2010 3:07 am
If you have a column with duplicated values, and you want to know what are those duplicated
values are and how many duplicates are there for each of those values, you can use the GROUP
BY ... HAVING clause as shown in the following example. It returns how many duplicated first
names in the employees table:
SQL> SELECT first_name, COUNT(*) FROM employees
GROUP BY first_name HAVING COUNT(*) > 1;
FIRST_NAME COUNT(*)
-------------------- ----------
Peter 3
Michael 2
Steven 2
John 3
Julia 2
William 2
Karen 2
Kevin 2
values are and how many duplicates are there for each of those values, you can use the GROUP
BY ... HAVING clause as shown in the following example. It returns how many duplicated first
names in the employees table:
SQL> SELECT first_name, COUNT(*) FROM employees
GROUP BY first_name HAVING COUNT(*) > 1;
FIRST_NAME COUNT(*)
-------------------- ----------
Peter 3
Michael 2
Steven 2
John 3
Julia 2
William 2
Karen 2
Kevin 2
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