Corruption and Repairs

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mysqlcheck -options database

-c	Checks tables for errors. It performs a `CHECK TABLE` operation on each table in the specified databases.
-r	Attempts to repair corrupted tables. It performs a `REPAIR TABLE` operation on each corrupted table.
-a	Analyzes tables for optimal performance. It performs an `ANALYZE TABLE` operation on each table.
-o	Optimizes tables to reduce fragmentation and reclaim unused space. It performs an `OPTIMIZE TABLE` operation on each table.
--databases db1 db2	Checks and repairs tables in multiple databases (`db1` and `db2`).
-A	Checks and repairs tables in all databases on the MySQL server.

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Table Corruption: Use mysqlcheck -r (or mysqlcheck --repair) when you suspect or know that one or more tables in your MySQL database are corrupted or have crashed.
Error Messages: If MySQL reports errors such as "table is marked as crashed" or "table needs repair," mysqlcheck -r is a suitable approach to attempt repair.

Backup: Always make a backup of your databases before attempting any repairs. While mysqlcheck -r is generally safe, there is a small risk of data loss if the repair process encounters unexpected issues.
Table Locking: During repair, mysqlcheck will lock tables to ensure data consistency. Depending on the size and activity of your database, this can cause downtime or impact performance.

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