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我們知道，MySQL數(shù)據(jù)庫的每一個數(shù)據(jù)庫對應(yīng)一個子目錄，每個子目錄中包含了對應(yīng)于這個數(shù)據(jù)庫中的數(shù)據(jù)表的文件。每一個數(shù)據(jù)表對應(yīng)三個文件，它們和表名相同，但是具有不同的擴(kuò)展名。tblName.frm文件是表的定義，它保存了表中包含的數(shù)據(jù)列的內(nèi)容和類型。tblName.MYD文件包含了表中的數(shù)據(jù)。tblName.MYI文件包含了表的索引(例如，它可能包含lookup表以幫助提高對表的主鍵列的查詢)。
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要檢查一個表的錯誤，只需要運行myisamchk(在MySQL的bin目錄下)并提供文件的位置和表名，或者是表的索引文件名：
- % myisamchk /usr/local/mysql/var/dbName/tblName
- % myisamchk /usr/local/mysql/var/dbName/tblName.MYI
上面的兩個命令都可以執(zhí)行對指定表的檢查。要檢查數(shù)據(jù)庫中所有的表，可以使用通配符：
- % myisamchk /usr/local/mysql/var/dbName*.MYI
如果不帶任何選項，myisamchk將對表文件執(zhí)行普通的檢查。如果你對一個表有懷疑，但是普通的檢查不能發(fā)現(xiàn)任何錯誤，你可以執(zhí)行更徹底的檢查(但是也更慢！)，這需要使用--extend-check選項：
- % myisamchk --extend-check /path/to/tblName
對錯誤的檢查是沒有破壞性的，這意味著你不必?fù)?dān)心執(zhí)行對你的數(shù)據(jù)文件的檢查會使已經(jīng)存在的問題變得更糟。另一方面，修復(fù)選項，雖然通常也是安全的，但是它對你的數(shù)據(jù)文件的更改是無法撤消的。因為這個原因，我們強(qiáng)烈推薦你試圖修復(fù)一個被破壞的表文件時首先做個備份，并確保在制作這個備份之前你的MySQL服務(wù)是關(guān)閉的。
在windows 2003下通過命令提示符，輸入：
注：此為記錄我當(dāng)時操作的全部過程
- 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' 不是內(nèi)部或外部命令，也不是可運行的程序或批處理文件。
- C:\mysql\data\hw_enterprice>cd\
- C:\>cd mysql
- C:\mysql>cd bin
注：查看myisamchk的幫助信息
- 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"
繼續(xù)進(jìn)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
系統(tǒng)提示我使用--safe-recover (-o) or the --force (-f) option進(jìn)行修復(fù)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
將修復(fù)后的物理文件復(fù)制到mysql\data下之后，通過phpMyAdmin進(jìn)行訪問，OK正常！
本次數(shù)據(jù)修復(fù)操作成功，數(shù)據(jù)已被正常恢復(fù)，總計85215條記錄，其中恢復(fù)數(shù)據(jù)共計85207條。
總結(jié)本次經(jīng)驗及查找資料，如下：
當(dāng)你試圖修復(fù)一個被破壞的表的問題時，有三種修復(fù)類型。如果你得到一個錯誤信息指出一個臨時文件不能建立，刪除信息所指出的文件并再試一次--這通常是上一次修復(fù)操作遺留下來的。
這三種修復(fù)方法如下所示：
- % myisamchk --recover --quick /path/to/tblName
- % myisamchk --recover /path/to/tblName
- % myisamchk --safe-recover /path/to/tblName
第一種是最快的，用來修復(fù)最普通的問題；而最后一種是最慢的，用來修復(fù)一些其它方法所不能修復(fù)的問題。
檢查和修復(fù)MySQL數(shù)據(jù)文件
如果上面的方法無法修復(fù)一個被損壞的表，在你放棄之前，你還可以試試下面這兩個技巧：
如果你懷疑表的索引文件(*.MYI)發(fā)生了不可修復(fù)的錯誤，甚至是丟失了這個文件，你可以使用數(shù)據(jù)文件(*.MYD)和數(shù)據(jù)格式文件(*.frm)重新生成它。首先制作一個數(shù)據(jù)文件(tblName.MYD)的拷貝。重啟你的MySQL服務(wù)并連接到這個服務(wù)上，使用下面的命令刪除表的內(nèi)容：mysql> DELETE FROM tblName;
在刪除表的內(nèi)容的同時，會建立一個新的索引文件。退出登錄并重新關(guān)閉服務(wù)，然后用你剛才保存的數(shù)據(jù)文件(tblName.MYD)覆蓋新的(空)數(shù)據(jù)文件。最后，使用myisamchk執(zhí)行標(biāo)準(zhǔn)的修復(fù)(上面的第二種方法)，根據(jù)表的數(shù)據(jù)的內(nèi)容和表的格式文件重新生成索引數(shù)據(jù)。
如果你的表的格式文件(tblName.frm)丟失了或者是發(fā)生了不可修復(fù)的錯誤，但是你清楚如何使用相應(yīng)的CREATE TABLE語句來重新生成這張表，你可以重新生成一個新的.frm文件并和你的數(shù)據(jù)文件和索引文件(如果索引文件有問題，使用上面的方法重建一個新的)一起使用。首先制作一個數(shù)據(jù)和索引文件的拷貝，然后刪除原來的文件(刪除數(shù)據(jù)目錄下有關(guān)這個表的所有記錄)。
啟動MySQL服務(wù)并使用當(dāng)初的CREATE TABLE文件建立一個新的表。新的.frm文件應(yīng)該可以正常工作了，但是最好你還是執(zhí)行一下標(biāo)準(zhǔn)的修復(fù)(上面的第二種方法)。
關(guān)于MySQL數(shù)據(jù)庫.frm .MYD .MYI損壞的修復(fù)方法就介紹到這里了，希望本次的介紹能夠給您帶來一些收獲！
本文標(biāo)題：MySQL數(shù)據(jù)庫.frm文件、.MYD文件和.MYI文件的修復(fù)方法
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