There can be scenarios where tables in databases can become corrupted due to various reasons such as hardware failures, software bugs, or unexpected server crashes. When this situation happens, we cannot be able to access or manipulate the data in those tables because of data inconsistencies or errors.
The QUICK clause is the is the default and it is most commonly used with REPAIR TABLE. If you specify the QUICK clause, MySQL will repair the table without re-creating it.
If we specify the EXTENDED clause, MySQL not only repairs the table but also rebuilds the index and optimizes the table structure.
We can use the USE_FRM clause, in case the MYI index file is missing. If you provide this clause the .NYI file will be recreated using information from the data dictionary