How to determine if an index exists in SQL?

In SQL, you can use the following statement to check if an index exists:

SHOW INDEX FROM table_name WHERE Key_name = 'index_name';

The table_name is the name of the table, and index_name is the name of the index.

If the statement returns a result set, it means the index exists; if the result set is empty, it means the index does not exist.