mariadb check for duplicate code example

Example 1: find duplicate keys in mysql

SELECT col, COUNT(col) FROM table_name GROUP BY col HAVING COUNT(col) > 1;

Example 2: 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);