SpirirHost Support Centre: MySQL Reference Manual p.230

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Table of Contents
1. General Information
2. MySQL Installation
3. Tutorial Introduction
4. Database Administration
5. MySQL Optimisation
6. MySQL Language Reference
7. MySQL Table Types
8. MySQL APIs
9. Extending MySQL

230 MySQL Technical Reference for Version 4.0.3 MEDIUM Scan rows to verify that deleted links are okay. This also calculates a key checksum for the rows and veries this with a calcualted checksum for the keys. EXTENDED Do a full key lookup for all keys for each row. This ensures that the table is 100% consistent, but will take a long time! For dynamically sized MyISAM tables a started check will always do a MEDIUM check. For static size rows we skip the row scan for QUICK and FAST as the rows are very seldom corrupted. You can combine check options as in: CHECK TABLE test_table FAST QUICK; Which would simply do a quick check on the table to see whether it was closed properly. Note: that in some case CHECK TABLE will change the table! This happens if the table is marked as 'corrupted' or 'not closed properly' but CHECK TABLE didn't nd any problems in the table. In this case CHECK TABLE will mark the table as okay. If a table is corrupted, then it's most likely that the problem is in the indexes and not in the data part. All of the above check types checks the indexes thoroughly and should thus nd most errors. If you just want to check a table that you assume is okay, you should use no check options or the QUICK option. The latter should be used when you are in a hurry and can take the very small risk that QUICK didn't nd an error in the datale. (In most cases MySQL should nd, under normal usage, any error in the data le. If this happens then the table will be marked as 'corrupted', in which case the table can't be used until it's repaired.) FAST and CHANGED are mostly intended to be used from a script (for example to be executed from cron) if you want to check your table from time to time. In most cases you FAST is to be prefered over CHANGED. (The only case when it isn't is when you suspect a bug you have found a bug in the MyISAM code.) EXTENDED is only to be used after you have run a normal check but still get strange errors from a table when MySQL tries to update a row or nd a row by key (this is very unlikely if a normal check has succeeded!). Some things reported by check table, can't be corrected automatically: Found row where the auto_increment column has the value 0. This means that you have in the table a row where the AUTO_INCREMENT index column contains the value 0. (It's possible to create a row where the AUTO_INCREMENT column is 0 by explicitly setting the column to 0 with an UPDATE statement) This isn't an error in itself, but could cause trouble if you decide to dump the table and restore it or do an ALTER TABLE on the table. In this case the AUTO_INCREMENT column will change value, according to the rules of AUTO_INCREMENT columns, which could cause problems like a duplicate key error. To get rid of the warning, just execute an UPDATE statement to set the column to some other value than 0. 4.4.5 REPAIR TABLE Syntax

MySQL Reference Manual

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