Insert into without duplicates

INSERT INTO  TableDuplicates
(empId)
SELECT  empId
FROM TableEmployees
WHERE empId NOT IN (select empId from TableDuplicates)

Get duplicates records in SQL

What are we cooking today? A query to count duplicates

SELECT ColumnX, COUNT(*) as  TotalCount
FROM TableY
GROUP BY  ColumnX 
HAVING COUNT(*) > 1
ORDER BY COUNT(*) DESC