When should you consider adding an index to a column in MySQL, and what are some scenarios where indexing might be detrimental?

You should consider indexing columns that are frequently used in `WHERE` clauses (for filtering), `JOIN` conditions, `ORDER BY` clauses (for sorting), `GROUP BY` clauses, or `DISTINCT` operations. Columns with high cardinality (many unique values) are generally good candidates. Indexing might be detrimental if: 1. The table is small, where a full table scan is often faster or comparable. 2. The column has very low cardinality (few unique values), making the index less selective and inefficient. 3. The table experiences very frequent `INSERT`, `UPDATE`, or `DELETE` operations, as each modification requires updating all associated indexes, adding significant overhead and slowing down DML operations. 4. You have too many indexes, which consume disk space and memory, and increase DML overhead.