How can you query duplicate data in a mysql database?

You can use the GROUP BY and HAVING clauses to check for duplicate data in MySQL. Here is an example query:

SELECT column_name, COUNT(column_name) as count
FROM table_name
GROUP BY column_name
HAVING count > 1;

Please replace the column_name with the field name to be checked for duplicates, and table_name with the table name to be queried.

This search will return duplicate data in the specified field and display the number of duplicates.