3) How to find duplicates in a table?
To find duplicates in the table , we can use group by function on those columns which are to be used and then listing them if their count is >1 .
Following sample query can be used to find duplicates in table having 3 columns
select col1, col2,col3, count(*) from table
group by col1, col2, col3
having count (*) > 1 ;