Why Does My MySQL Table Exist Yet Doesn\'t Exist?

Schrödinger's MySQL Table: An Enigma of Existence

Encountering the infamous "table already exists" error while attempting to create or alter a table, only to face the "unknown table" conundrum when trying to drop it, poses a perplexing dilemma. This paradoxical state, where a table seemingly exists yet eludes all attempts at manipulation, can leave database administrators bewildered.

The root of this enigmatic phenomenon lies in the missing or corrupted files in the data directory. When using InnoDB with innodb_file_per_table enabled, each table is represented by two files: a .frm file containing the table definition and an .ibd file storing its data. For MYISAM tables, the file trio consists of .frm, .MYI, and .MYD files.

When such files go missing or become damaged, the system may exhibit conflicting behavior. For instance, the table definition file might remain, leading to the "table already exists" error upon attempted creation. However, the absence of data or index files would result in the "unknown table" error when trying to drop it.

To resolve this issue, the solution is simple yet meticulous: locate the orphaned files and remove them manually. By deleting the missing .frm, .ibd, .MYI, or .MYD files, you can rectify the discrepancy and restore the expected behavior.

So, in the Schrödingerian realm of MySQL, where tables exist and yet do not, the key to resolving the paradox lies in diligently scrutinizing the data directory and ensuring the presence of all necessary files. By deleting the orphaned files, you can restore harmony to your database and bid farewell to the perplexing enigma of Schrödinger's table.

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