I have a table (employees) without a primary key. I want to make the emp_email_address field the primary key, only problem is, several records already share the same emp_email_address. How do I write a query which will show me all the instances where emp_ email_address is duplicated throughout the table.
Something like the following query should help you find all of the duplicate records:
SELECT emp_email_address FROM table GROUP BY emp_email_address HAVING COUNT(*)>1;