how to handle duplicate entry in mysql code example

Example 1: select where duplicate mysql

SELECT 
    col1, COUNT(col1),
    col2, COUNT(col2)
FROM
    table_name
GROUP BY 
    col1, 
    col2
HAVING 
       (COUNT(col1) > 1) AND 
       (COUNT(col2) > 1);

Example 2: duplicate row mysql

# Duplicate rows or row
INSERT INTO table (col1, col2, col3)
SELECT col1, col2, col3 FROM table
WHERE something...;