我们知道,MySQL数据库的每一个数据库对应一个子目录,每个子目录中包含了对应于这个数据库中的数据表的文件。每一个数据表对应三个文件,它们和表名相同,但是具有不同的扩展名。tblName.frm文件是表的定义,它保存了表中包含的数据列的内容和类型。tblName.MYD文件包含了表中的数据。tblName.MYI文件包含了表的索引(例如,它可能包含lookup表以帮助提高对表的主键列的查询)。
要检查一个表的错误,只需要运行myisamchk(在MySQL的bin目录下)并提供文件的位置和表名,或者是表的索引文件名:
class="dp-xml">
- % myisamchk /usr/local/mysql/var/dbName/tblName
- % myisamchk /usr/local/mysql/var/dbName/tblName.MYI
上面的两个命令都可以执行对指定表的检查。要检查数据库中所有的表,可以使用通配符:
- % myisamchk /usr/local/mysql/var/dbName*.MYI
如果不带任何选项,myisamchk将对表文件执行普通的检查。如果你对一个表有怀疑,但是普通的检查不能发现任何错误,你可以执行更彻底的检查(但是也更慢!),这需要使用--extend-check选项:
- % myisamchk --extend-check /path/to/tblName
对错误的检查是没有破坏性的,这意味着你不必担心执行对你的数据文件的检查会使已经存在的问题变得更糟。另一方面,修复选项,虽然通常也是安全的,但是它对你的数据文件的更改是无法撤消的。因为这个原因,我们强烈推荐你试图修复一个被破坏的表文件时首先做个备份,并确保在制作这个备份之前你的MySQL服务是关闭的。
在windows 2003下通过命令提示符,输入:
注:此为记录我当时操作的全部过程
- D:\Documents and Settings\Administrator>c:
- C:\>cd mysql
- C:\mysql>cd data
- C:\mysql\data>cd hw_enterprice
- C:\mysql\data\hw_enterprice>myisamchk function_products.frm
'myisamchk' 不是内部或外部命令,也不是可运行的程序或批处理文件。
- C:\mysql\data\hw_enterprice>cd\
- C:\>cd mysql
- C:\mysql>cd bin
注:查看myisamchk的帮助信息
- C:\mysql\bin>myisamchk
- myisamchk Ver 2.6 for Win95/Win98 at i32
- By Monty, for your professional use
- This software comes with NO WARRANTY: see the PUBLIC for details.
- Description, check and repair of ISAM tables.
- Used without options all tables on the command will be checked for errors
- Usage: myisamchk [OPTIONS] tables[.MYI]
- Global options:
- -#, --debug=... Output debug log. Often this is 'd:t:o,filename'
- -?, --help Display this help and exit.
- -O, --set-variable var=option
- Change the value of a variable. Please note that
- this option is deprecated; you can set variables
- directly with '--variable-name=value'.
- -t, --tmpdir=path Path for temporary files
- -s, --silent Only print errors. One can use two -s to make
- myisamchk very silent
- -v, --verbose Print more information. This can be used with
- --description and --check. Use many -v for more verbosity!
- -V, --version Print version and exit.
- -w, --wait Wait if table is locked.
- Check options (check is the default action for myisamchk):
- -c, --check Check table for errors
- -e, --extend-check Check the table VERY throughly. Only use this in
- extreme cases as myisamchk should normally be able to
- find out if the table is ok even without this switch
- -F, --fast Check only tables that haven't been closed properly
- -C, --check-only-changed
- Check only tables that have changed since last check
- -f, --force Restart with '-r' if there are any errors in the table.
- States will be updated as with '--update-state'
- -i, --information Print statistics information about table that is checked
- -m, --medium-check Faster than extend-check, but only finds 99.99% of
- all errors. Should be good enough for most cases
- -U --update-state Mark tables as crashed if you find any errors
- -T, --read-only Don't mark table as checked
- Repair options (When using '-r' or '-o')
- -B, --backup Make a backup of the .MYD file as 'filename-time.BAK'
- --correct-checksum Correct checksum information for table.
- -D, --data-file-length=# Max length of data file (when recreating data
- file when it's full)
- -e, --extend-check Try to recover every possible row from the data file
- Normally this will also find a lot of garbage rows;
- Don't use this option if you are not totally desperate.
- -f, --force Overwrite old temporary files.
- -k, --keys-used=# Tell MyISAM to update only some specific keys. # is a
- bit mask of which keys to use. This can be used to
- get faster inserts!
- -r, --recover Can fix almost anything except unique keys that aren't
- unique.
- -n, --sort-recover Forces recovering with sorting even if the temporary
- file would be very big.
- -p, --parallel-recover
- Uses the same technique as '-r' and '-n', but creates
- all the keys in parallel, in different threads.
- THIS IS ALPHA CODE. USE AT YOUR OWN RISK!
- -o, --safe-recover Uses old recovery method; Slower than '-r' but can
- handle a couple of cases where '-r' reports that it
- can't fix the data file.
- --character-sets-dir=...
- Directory where character sets are
- --set-character-set=name
- Change the character set used by the index
- -q, --quick Faster repair by not modifying the data file.
- One can give a second '-q' to force myisamchk to
- modify the original datafile in case of duplicate keys
- -u, --unpack Unpack file packed with myisampack.
- Other actions:
- -a, --analyze Analyze distribution of keys. Will make some joins in
- MySQL faster. You can check the calculated distribution
- by using '--description --verbose table_name'.
- -d, --description Prints some information about table.
- -A, --set-auto-increment[=value]
- Force auto_increment to start at this or higher value
- If no value is given, then sets the next auto_increment
- value to the highest used value for the auto key + 1.
- -S, --sort-index Sort index blocks. This speeds up 'read-next' in
- applications
- -R, --sort-records=#
- Sort records according to an index. This makes your
- data much more localized and may speed up things
- C:\mysql\bin>myisamchk c:\mysql\data\hw_enterprice\function_products.frm
- myisamchk: error: 'c:\mysql\data\hw_enterprice\function_products.frm' is not a M
- yISAM-table
- C:\mysql\bin>myisamchk c:\mysql\data\hw_enterprice\function_products.myi
- Checking MyISAM file: c:\mysql\data\hw_enterprice\function_products.myi
- Data records: 85207 Deleted blocks: 39
- myisamchk: warning: Table is marked as crashed
- myisamchk: warning: 1 clients is using or hasn't closed the table properly
- - check file-size
- - check key delete-chain
- - check record delete-chain
- myisamchk: error: record delete-link-chain corrupted
- - check index reference
- - check data record references index: 1
- - check data record references index: 2
- - check data record references index: 3
- - check record links
- myisamchk: error: Wrong bytesec: 0-195-171 at linkstart: 841908
- MyISAM-table 'c:\mysql\data\hw_enterprice\function_products.myi' is corrupted
- Fix it using switch "-r" or "-o"
继续进行操作:
- C:\mysql\bin>myisamchk --recover --quick c:\mysql\data\hw_enterprice\function_p
- roducts.myi
- - check key delete-chain
- - check record delete-chain
- myisamchk: error: record delete-link-chain corrupted
- myisamchk: error: Quick-recover aborted; Run recovery without switch 'q'
- Updating MyISAM file: c:\mysql\data\hw_enterprice\function_products.myi
- MyISAM-table 'c:\mysql\data\hw_enterprice\function_products.myi' is not fixed be
- cause of errors
- Try fixing it by using the --safe-recover (-o) or the --force (-f) option
系统提示我使用--safe-recover (-o) or the --force (-f) option进行修复操作,于是
- C:\mysql\bin>myisamchk --safe-recover c:\mysql\data\hw_enterprice\function_prod
- ucts.myi
- - recovering (with keycache) MyISAM-table 'c:\mysql\data\hw_enterprice\function_
- products.myi'
- Data records: 85207
- Wrong bytesec: 0-195-171 at 841908; Skipped
- Data records: 85215
将修复后的物理文件复制到mysql\data下之后,通过phpMyAdmin进行访问,OK正常!
本次数据修复操作成功,数据已被正常恢复,总计85215条记录,其中恢复数据共计85207条。
总结本次经验及查找资料,如下:
当你试图修复一个被破坏的表的问题时,有三种修复类型。如果你得到一个错误信息指出一个临时文件不能建立,删除信息所指出的文件并再试一次--这通常是上一次修复操作遗留下来的。
这三种修复方法如下所示:
- % myisamchk --recover --quick /path/to/tblName
- % myisamchk --recover /path/to/tblName
- % myisamchk --safe-recover /path/to/tblName
第一种是最快的,用来修复最普通的问题;而最后一种是最慢的,用来修复一些其它方法所不能修复的问题。
检查和修复MySQL数据文件
如果上面的方法无法修复一个被损坏的表,在你放弃之前,你还可以试试下面这两个技巧:
如果你怀疑表的索引文件(*.MYI)发生了不可修复的错误,甚至是丢失了这个文件,你可以使用数据文件(*.MYD)和数据格式文件(*.frm)重新生成它。首先制作一个数据文件(tblName.MYD)的拷贝。重启你的MySQL服务并连接到这个服务上,使用下面的命令删除表的内容:mysql> DELETE FROM tblName;
在删除表的内容的同时,会建立一个新的索引文件。退出登录并重新关闭服务,然后用你刚才保存的数据文件(tblName.MYD)覆盖新的(空)数据文件。最后,使用myisamchk执行标准的修复(上面的第二种方法),根据表的数据的内容和表的格式文件重新生成索引数据。
如果你的表的格式文件(tblName.frm)丢失了或者是发生了不可修复的错误,但是你清楚如何使用相应的CREATE TABLE语句来重新生成这张表,你可以重新生成一个新的.frm文件并和你的数据文件和索引文件(如果索引文件有问题,使用上面的方法重建一个新的)一起使用。首先制作一个数据和索引文件的拷贝,然后删除原来的文件(删除数据目录下有关这个表的所有记录)。
启动MySQL服务并使用当初的CREATE TABLE文件建立一个新的表。新的.frm文件应该可以正常工作了,但是最好你还是执行一下标准的修复(上面的第二种方法)。
关于MySQL数据库.frm .MYD .MYI损坏的修复方法就介绍到这里了,希望本次的介绍能够给您带来一些收获!