topic：【原创】假设在有最后一次全库备份之后，你误删除了一张表，请使用备份+归档来将数据库恢复到删除表之前的状态。(不完全恢复)更多精彩内容尽在www.leonar
topic：【原创】假设在有最后一次全库备份之后，你误删除了一张表，请使用备份+归档来将数据库恢复到删除表之前的状态。(不完全恢复)
更多精彩内容尽在
进入Rman做全库备份
[oracle@leonarding1backup]$ rman target /
Recovery Manager:Release 11.2.0.1.0 - Production on Tue Apr 30 11:08:29 2013
Copyright (c)1982, 2009, Oracle and/or its affiliates. All rights reserved.
connected totarget database: LEO1 (DBID=1692458681)
RMAN> backupfull database format
'/u02/app/oracle/backup/full_bk1_%u%p%s.rmn'include current controlfile
plus
archivelog format'/u02/app/oracle/backup/arch_bk1_%u%p%s.rmn' delete all input;
2> 3> 4>
Starting backup at30-APR-13
current logarchived
using targetdatabase control file instead of recovery catalog
allocated channel:ORA_DISK_1
channelORA_DISK_1: SID=22 device type=DISK
RMAN-00571:===========================================================
RMAN-00569:=============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571:===========================================================
RMAN-03002:failure of backup plus archivelog command at 04/30/2013 11:13:27
RMAN-06059:expected archived log not found, loss of archived log compromisesrecoverability
ORA-19625: erroridentifying file /u02/app/oracle/archdata/1_75_813654649.dbf
ORA-27037: unableto obtain file status
Linux-x86_64Error: 2: No such file or directory
Additionalinformation: 3
75号归档日志缺失，Rman在操作系统上找不到对应的日志文件
当手工删除了归档日志以后，Rman备份会检测到日志缺失，从而无法进一步继续执行。
所以此时需要手工执行crosscheck过程，之后Rman备份可以恢复正常
RMAN> crosscheckarchivelog all; 交叉检查，有3个日志被手工删除
released channel:ORA_DISK_1
allocated channel:ORA_DISK_1
channelORA_DISK_1: SID=22 device type=DISK
validation failedfor archived log
archivedlog file name=/u02/app/oracle/archdata/1_75_813654649.dbf RECID=9STAMP=813790708
validation failedfor archived log
archivedlog file name=/u02/app/oracle/archdata/1_76_813654649.dbf RECID=7STAMP=813790702
validation failedfor archived log
archivedlog file name=/u02/app/oracle/archdata/1_77_813654649.dbf RECID=8STAMP=813790706
validationsucceeded for archived log
archived log filename=/u02/app/oracle/archdata/1_1_813790699.dbf RECID=10 STAMP=813791152
validationsucceeded for archived log
archived log filename=/u02/app/oracle/archdata/1_2_813790699.dbf RECID=11 STAMP=813913400
validationsucceeded for archived log
archived log filename=/u02/app/oracle/archdata/1_3_813790699.dbf RECID=12 STAMP=813913401
validationsucceeded for archived log
archived log filename=/u02/app/oracle/archdata/1_4_813790699.dbf RECID=13 STAMP=813913405
validationsucceeded for archived log
archived log filename=/u02/app/oracle/archdata/1_5_813790699.dbf RECID=14 STAMP=813933703
validationsucceeded for archived log
archived log filename=/u02/app/oracle/archdata/1_6_813790699.dbf RECID=15 STAMP=813933734
validationsucceeded for archived log
archived log filename=/u02/app/oracle/archdata/1_7_813790699.dbf RECID=16 STAMP=814090435
validationsucceeded for archived log
archived log filename=/u02/app/oracle/archdata/1_8_813790699.dbf RECID=17 STAMP=814090645
validationsucceeded for archived log
archived log filename=/u02/app/oracle/archdata/1_9_813790699.dbf RECID=18 STAMP=814090877
validationsucceeded for archived log
archived log filename=/u02/app/oracle/archdata/1_10_813790699.dbf RECID=19 STAMP=814091008
validationsucceeded for archived log
archived log filename=/u02/app/oracle/archdata/1_11_813790699.dbf RECID=20 STAMP=814091028
validationsucceeded for archived log
archived log filename=/u02/app/oracle/archdata/1_12_813790699.dbf RECID=21 STAMP=814091032
validationsucceeded for archived log
archived log filename=/u02/app/oracle/archdata/1_13_813790699.dbf RECID=22 STAMP=814091036
validationsucceeded for archived log
archived log filename=/u02/app/oracle/archdata/1_14_813790699.dbf RECID=23 STAMP=814091057
validationsucceeded for archived log
archived log filename=/u02/app/oracle/archdata/1_15_813790699.dbf RECID=24 STAMP=814091184
validationsucceeded for archived log
archived log filename=/u02/app/oracle/archdata/1_16_813790699.dbf RECID=25 STAMP=814091638
validationsucceeded for archived log
archived log filename=/u02/app/oracle/archdata/1_17_813790699.dbf RECID=26 STAMP=814091658
validationsucceeded for archived log
archived log filename=/u02/app/oracle/archdata/1_18_813790699.dbf RECID=27 STAMP=814091709
validationsucceeded for archived log
archived log filename=/u02/app/oracle/archdata/1_19_813790699.dbf RECID=28 STAMP=814092394
validationsucceeded for archived log
archived log filename=/u02/app/oracle/archdata/1_20_813790699.dbf RECID=29 STAMP=814092405
validationsucceeded for archived log
archived log filename=/u02/app/oracle/archdata/1_1_814098124.dbf RECID=30 STAMP=814098353
validationsucceeded for archived log
archived log filename=/u02/app/oracle/archdata/1_2_814098124.dbf RECID=31 STAMP=814100979
validationsucceeded for archived log
archived log filename=/u02/app/oracle/archdata/1_3_814098124.dbf RECID=32 STAMP=814101206
validationsucceeded for archived log
archived log filename=/u02/app/oracle/archdata/1_4_814098124.dbf RECID=33 STAMP=814101824
Crosschecked 27objects
RMAN> deleteexpired archivelog all; 删除所有过期归档日志
released channel:ORA_DISK_1
allocated channel:ORA_DISK_1
channelORA_DISK_1: SID=22 device type=DISK
List of ArchivedLog Copies for database with db_unique_name LEO1
=====================================================================
Key Thrd Seq S Low Time
------- ----------- - ---------
9 1 75 X 26-APR-13
Name: /u02/app/oracle/archdata/1_75_813654649.dbf
7 1 76 X 26-APR-13
Name: /u02/app/oracle/archdata/1_76_813654649.dbf
8 1 77 X 26-APR-13
Name: /u02/app/oracle/archdata/1_77_813654649.dbf
Do you really wantto delete the above objects (enter YES or NO)? y 75 76 77号日志被删除
deleted archivedlog
archived log filename=/u02/app/oracle/archdata/1_75_813654649.dbf RECID=9 STAMP=813790708
deleted archivedlog
archived log filename=/u02/app/oracle/archdata/1_76_813654649.dbf RECID=7 STAMP=813790702
deleted archivedlog
archived log filename=/u02/app/oracle/archdata/1_77_813654649.dbf RECID=8 STAMP=813790706
Deleted 3 EXPIREDobjects
RMAN> backup fulldatabase format 现在Rman备份可以恢复正常，同时删除备份过的归档日志
'/u02/app/oracle/backup/full_bk1_%u%p%s.rmn'include current controlfile
plus
archivelog format'/u02/app/oracle/backup/arch_bk1_%u%p%s.rmn' delete all input;2> 3> 4>
Starting backup at30-APR-13
current logarchived
using channelORA_DISK_1
channelORA_DISK_1: starting archived log backup set
channelORA_DISK_1: specifying archived log(s) in backup set
input archived logthread=1 sequence=1 RECID=10 STAMP=813791152
input archived logthread=1 sequence=2 RECID=11 STAMP=813913400
input archived logthread=1 sequence=3 RECID=12 STAMP=813913401
input archived logthread=1 sequence=4 RECID=13 STAMP=813913405
input archived logthread=1 sequence=5 RECID=14 STAMP=813933703
input archived logthread=1 sequence=6 RECID=15 STAMP=813933734
input archived logthread=1 sequence=7 RECID=16 STAMP=814090435
input archived logthread=1 sequence=8 RECID=17 STAMP=814090645
input archived logthread=1 sequence=9 RECID=18 STAMP=814090877
input archived logthread=1 sequence=10 RECID=19 STAMP=814091008
input archived logthread=1 sequence=11 RECID=20 STAMP=814091028
input archived logthread=1 sequence=12 RECID=21 STAMP=814091032
input archived logthread=1 sequence=13 RECID=22 STAMP=814091036
input archived logthread=1 sequence=14 RECID=23 STAMP=814091057
input archived logthread=1 sequence=15 RECID=24 STAMP=814091184
input archived logthread=1 sequence=16 RECID=25 STAMP=814091638
input archived logthread=1 sequence=17 RECID=26 STAMP=814091658
input archived logthread=1 sequence=18 RECID=27 STAMP=814091709
input archived logthread=1 sequence=19 RECID=28 STAMP=814092394
channelORA_DISK_1: starting piece 1 at 30-APR-13
channelORA_DISK_1: finished piece 1 at 30-APR-13
piecehandle=/u02/app/oracle/backup/arch_bk1_0co8cds4112.rmn tag=TAG20130430T113324comment=NONE
channelORA_DISK_1: backup set complete, elapsed time: 00:00:07
channelORA_DISK_1: deleting archived log(s)
archived log filename=/u02/app/oracle/archdata/1_1_813790699.dbf RECID=10 STAMP=813791152
archived log filename=/u02/app/oracle/archdata/1_2_813790699.dbf RECID=11 STAMP=813913400
archived log filename=/u02/app/oracle/archdata/1_3_813790699.dbf RECID=12 STAMP=813913401
archived log filename=/u02/app/oracle/archdata/1_4_813790699.dbf RECID=13 STAMP=813913405
archived log filename=/u02/app/oracle/archdata/1_5_813790699.dbf RECID=14 STAMP=813933703
archived log filename=/u02/app/oracle/archdata/1_6_813790699.dbf RECID=15 STAMP=813933734
archived log filename=/u02/app/oracle/archdata/1_7_813790699.dbf RECID=16 STAMP=814090435
archived log filename=/u02/app/oracle/archdata/1_8_813790699.dbf RECID=17 STAMP=814090645
archived log filename=/u02/app/oracle/archdata/1_9_813790699.dbf RECID=18 STAMP=814090877
archived log filename=/u02/app/oracle/archdata/1_10_813790699.dbf RECID=19 STAMP=814091008
archived log filename=/u02/app/oracle/archdata/1_11_813790699.dbf RECID=20 STAMP=814091028
archived log filename=/u02/app/oracle/archdata/1_12_813790699.dbf RECID=21 STAMP=814091032
archived log filename=/u02/app/oracle/archdata/1_13_813790699.dbf RECID=22 STAMP=814091036
archived log filename=/u02/app/oracle/archdata/1_14_813790699.dbf RECID=23 STAMP=814091057
archived log filename=/u02/app/oracle/archdata/1_15_813790699.dbf RECID=24 STAMP=814091184
archived log filename=/u02/app/oracle/archdata/1_16_813790699.dbf RECID=25 STAMP=814091638
archived log filename=/u02/app/oracle/archdata/1_17_813790699.dbf RECID=26 STAMP=814091658
archived log filename=/u02/app/oracle/archdata/1_18_813790699.dbf RECID=27 STAMP=814091709
archived log filename=/u02/app/oracle/archdata/1_19_813790699.dbf RECID=28 STAMP=814092394
channelORA_DISK_1: starting archived log backup set
channelORA_DISK_1: specifying archived log(s) in backup set
input archived logthread=1 sequence=1 RECID=30 STAMP=814098353
channelORA_DISK_1: starting piece 1 at 30-APR-13
channelORA_DISK_1: finished piece 1 at 30-APR-13
piecehandle=/u02/app/oracle/backup/arch_bk1_0do8cdsc113.rmn tag=TAG20130430T113324comment=NONE
channelORA_DISK_1: backup set complete, elapsed time: 00:00:01
channelORA_DISK_1: deleting archived log(s)
archived log filename=/u02/app/oracle/archdata/1_1_814098124.dbf RECID=30 STAMP=814098353
channelORA_DISK_1: starting archived log backup set
channelORA_DISK_1: specifying archived log(s) in backup set
input archived logthread=1 sequence=20 RECID=29 STAMP=814092405
channelORA_DISK_1: starting piece 1 at 30-APR-13
channelORA_DISK_1: finished piece 1 at 30-APR-13
piecehandle=/u02/app/oracle/backup/arch_bk1_0eo8cdsd114.rmn tag=TAG20130430T113324comment=NONE
channelORA_DISK_1: backup set complete, elapsed time: 00:00:01
channelORA_DISK_1: deleting archived log(s)
archived log filename=/u02/app/oracle/archdata/1_20_813790699.dbf RECID=29 STAMP=814092405
channelORA_DISK_1: starting archived log backup set
channelORA_DISK_1: specifying archived log(s) in backup set
input archived logthread=1 sequence=2 RECID=31 STAMP=814100979
input archived logthread=1 sequence=3 RECID=32 STAMP=814101206
input archived logthread=1 sequence=4 RECID=33 STAMP=814101824
input archived logthread=1 sequence=5 RECID=34 STAMP=814102404
channelORA_DISK_1: starting piece 1 at 30-APR-13
channelORA_DISK_1: finished piece 1 at 30-APR-13
piecehandle=/u02/app/oracle/backup/arch_bk1_0fo8cdse115.rmn tag=TAG20130430T113324comment=NONE
channelORA_DISK_1: backup set complete, elapsed time: 00:00:01
channelORA_DISK_1: deleting archived log(s)
archived log filename=/u02/app/oracle/archdata/1_2_814098124.dbf RECID=31 STAMP=814100979
archived log filename=/u02/app/oracle/archdata/1_3_814098124.dbf RECID=32 STAMP=814101206
archived log filename=/u02/app/oracle/archdata/1_4_814098124.dbf RECID=33 STAMP=814101824
archived log filename=/u02/app/oracle/archdata/1_5_814098124.dbf RECID=34 STAMP=814102404
Finished backup at30-APR-13
Starting backup at30-APR-13
using channelORA_DISK_1
channelORA_DISK_1: starting full datafile backup set
channelORA_DISK_1: specifying datafile(s) in backup set
input datafilefile number=00001 name=/u02/app/oracle/oradata/LEO1/system01.dbf
input datafilefile number=00002 name=/u02/app/oracle/oradata/LEO1/sysaux01.dbf
input datafilefile number=00003 name=/u02/app/oracle/oradata/LEO1/undotbs01.dbf
input datafile filenumber=00005 name=/u02/app/oracle/oradata/LEO1/leo1.dbf
input datafilefile number=00004 name=/u02/app/oracle/oradata/LEO1/users01.dbf
channelORA_DISK_1: starting piece 1 at 30-APR-13
channelORA_DISK_1: finished piece 1 at 30-APR-13
piece handle=/u02/app/oracle/backup/full_bk1_0go8cdsg116.rmntag=TAG20130430T113336 comment=NONE
channelORA_DISK_1: backup set complete, elapsed time: 00:01:25
channelORA_DISK_1: starting full datafile backup set
channelORA_DISK_1: specifying datafile(s) in backup set
including currentcontrol file in backup set
channelORA_DISK_1: starting piece 1 at 30-APR-13
channelORA_DISK_1: finished piece 1 at 30-APR-13
piecehandle=/u02/app/oracle/backup/full_bk1_0ho8cdv5117.rmn tag=TAG20130430T113336comment=NONE
channel ORA_DISK_1:backup set complete, elapsed time: 00:00:01
Finished backup at30-APR-13
Starting backup at30-APR-13
current logarchived
using channelORA_DISK_1
channelORA_DISK_1: starting archived log backup set
channelORA_DISK_1: specifying archived log(s) in backup set
input archived logthread=1 sequence=6 RECID=35 STAMP=814102503
channelORA_DISK_1: starting piece 1 at 30-APR-13
channelORA_DISK_1: finished piece 1 at 30-APR-13
piecehandle=/u02/app/oracle/backup/arch_bk1_0io8cdv7118.rmn tag=TAG20130430T113503comment=NONE
channelORA_DISK_1: backup set complete, elapsed time: 00:00:01
channelORA_DISK_1: deleting archived log(s)
archived log filename=/u02/app/oracle/archdata/1_6_814098124.dbf RECID=35 STAMP=814102503
Finished backup at30-APR-13
Starting ControlFile and SPFILE Autobackup at 30-APR-13
piecehandle=/u02/app/oracle/backup/control/cf_c-1692458681-20130430-01 comment=NONE
Finished ControlFile and SPFILE Autobackup at 30-APR-13
我们现在进入数据库创建一个表leo1并插入三条记录
SYS@LEO1>createtable leo1 (name varchar2(20),age number,riqi date);
Table created.
SYS@LEO1>insertinto leo1 values('leonarding',28,sysdate);
1 row created.
SYS@LEO1>insertinto leo1 values('sun_vn',26,sysdate);
1 row created.
SYS@LEO1>insertinto leo1 values('tiger',18,sysdate);
1 row created.
SYS@LEO1>commit;
Commit complete.
SYS@LEO1>select* from leo1; 完成
NAME AGE RIQI
------------------------------ ---------
leonarding 28 30-APR-13
sun_vn 26 30-APR-13
tiger 18 30-APR-13
SYS@LEO1>selectgroup#,members,bytes,archived,sequence#,status from v$log;
GROUP# MEMBERS BYTES ARC SEQUENCE# STATUS
-------------------- ---------- --- ---------- ----------------
1 2 52428800 NO 7 CURRENT
2 2 52428800 YES 5 INACTIVE
5 2 52428800 YES 6 INACTIVE
我们创建表和插入信息是写入当前日志组1
SYS@LEO1>altersystem switch logfile; 切换日志组
System altered.
SYS@LEO1>altersystem switch logfile;
System altered.
SYS@LEO1>selectgroup#,members,bytes,archived,sequence#,status from v$log;
GROUP# MEMBERS BYTES ARC SEQUENCE# STATUS
-------------------- ---------- --- ---------- ----------------
1 2 52428800 YES 7 INACTIVE
2 2 52428800 YES 8 INACTIVE
5 2 52428800 NO 9 CURRENT
现在组1已经完成归档，如果我们此时勿删除了leo1表，我们可以把数据库恢复到7号归档日志的那一点，网站空间，就可以恢复勿删除的leo1表了。我们顺便把当前redolog日志也损坏了，看看可不可以扶起数据库来。
SYS@LEO1>droptable leo1 purge; 删除表
我们删除第五组的2个成员
[oracle@leonarding1LEO1]$ rm -rf redo05.log
[oracle@leonarding1LEO1]$ cd disk2/
[oracle@leonarding1disk2]$ rm -rf redo05_b.log
SYS@LEO1>startup
ORACLE instancestarted.
Total SystemGlobal Area 471830528 bytes
Fixed Size 2214456 bytes
Variable Size 171967944 bytes
DatabaseBuffers 289406976 bytes
Redo Buffers 8241152 bytes
Database mounted.
ORA-00313: openfailed for members of log group 5 of thread 1
ORA-00312: onlinelog 5 thread 1:
'/u02/app/oracle/oradata/LEO1/disk2/redo05_b.log'
ORA-27037: unableto obtain file status
Linux-x86_64Error: 2: No such file or directory
Additionalinformation: 3
ORA-00312: onlinelog 5 thread 1: '/u02/app/oracle/oradata/LEO1/redo05.log'
ORA-27037: unableto obtain file status
Linux-x86_64Error: 2: No such file or directory
Additionalinformation: 3
找不到第五组redo，实际上已经被我们删除了，进入rman进行恢复操作
[oracle@leonarding1backup]$ rman target /
Recovery Manager:Release 11.2.0.1.0 - Production on Tue Apr 30 12:47:55 2013
Copyright (c)1982, 2009, Oracle and/or its affiliates. All rights reserved.
connected totarget database: LEO1 (DBID=1692458681, not open)
RMAN> restoredatabase;
Starting restoreat 30-APR-13
using targetdatabase control file instead of recovery catalog
allocated channel:ORA_DISK_1
channelORA_DISK_1: SID=133 device type=DISK
channelORA_DISK_1: starting datafile backup set restore
channelORA_DISK_1: specifying datafile(s) to restore from backup set
channelORA_DISK_1: restoring datafile 00001 to/u02/app/oracle/oradata/LEO1/system01.dbf
channelORA_DISK_1: restoring datafile 00002 to/u02/app/oracle/oradata/LEO1/sysaux01.dbf
channelORA_DISK_1: restoring datafile 00003 to /u02/app/oracle/oradata/LEO1/undotbs01.dbf
channelORA_DISK_1: restoring datafile 00004 to/u02/app/oracle/oradata/LEO1/users01.dbf
channelORA_DISK_1: restoring datafile 00005 to /u02/app/oracle/oradata/LEO1/leo1.dbf
channelORA_DISK_1: reading from backup piece /u02/app/oracle/backup/full_bk1_0go8cdsg116.rmn
channelORA_DISK_1: piece handle=/u02/app/oracle/backup/full_bk1_0go8cdsg116.rmntag=TAG20130430T113336
channelORA_DISK_1: restored backup piece 1
channelORA_DISK_1: restore complete, elapsed time: 00:02:05
Finished restoreat 30-APR-13
我们只需恢复到7号归档日志状态点，就可以找回我们删除了的leo1表
RMAN> recoverdatabase until sequence 7 thread 1;
Starting recoverat 30-APR-13
using channelORA_DISK_1
starting mediarecovery
channelORA_DISK_1: starting archived log restore to default destination
channel ORA_DISK_1:restoring archived log
archived logthread=1 sequence=6
channelORA_DISK_1: reading from backup piece/u02/app/oracle/backup/arch_bk1_0io8cdv7118.rmn
channelORA_DISK_1: piece handle=/u02/app/oracle/backup/arch_bk1_0io8cdv7118.rmntag=TAG20130430T113503
channelORA_DISK_1: restored backup piece 1
channelORA_DISK_1: restore complete, elapsed time: 00:00:01
archived log filename=/u02/app/oracle/archdata/1_6_814098124.dbf thread=1 sequence=6
media recoverycomplete, elapsed time: 00:00:01
Finished recoverat 30-APR-13
SYS@LEO1>alterdatabase open resetlogs;
Database altered.
resetlogs做的几件事：
1）数据文件头scn号为准，同步控制文件和在线日志文件scn号
2）重新创建redolog日志（创建一个空日志），重置为unused
3）重置归档日志序号从1开始编码
4）让数据库重新进入一个新的生命周期
SYS@LEO1>select* from leo1;
NAME AGE RIQI
------------------------------ ---------
leonarding 28 30-APR-13
sun_vn 26 30-APR-13
tiger 18 30-APR-13
这个表存在说明应用了 sequence为7的归档
小结：到此我们的系列恢复实验完美完成，里面阐述了各种不同环境下的恢复测试，简明了重做日志和归档日志关系，在什么情况下可以恢复到什么级别，虚拟主机，牢实掌握如上信息，可以让你遇事不慌张事半功倍。
控制文件恢复，重做日志恢复，完全恢复，不完全恢复，备份
Leonarding
2013.4.30
天津&spring
分享技术~成就梦想
Blog：
本文出自 “leonarding Blog” 博客，请务必保留此出处
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MySQL索引基數如何影響查詢性能？Apr 14, 2025 am 12:18 AMMySQL索引基数对查询性能有显著影响：1.高基数索引能更有效地缩小数据范围，提高查询效率；2.低基数索引可能导致全表扫描，降低查询性能；3.在联合索引中，应将高基数列放在前面以优化查询。
MySQL：新用戶的資源和教程Apr 14, 2025 am 12:16 AMMySQL學習路徑包括基礎知識、核心概念、使用示例和優化技巧。 1)了解表、行、列、SQL查詢等基礎概念。 2)學習MySQL的定義、工作原理和優勢。 3)掌握基本CRUD操作和高級用法，如索引和存儲過程。 4)熟悉常見錯誤調試和性能優化建議，如合理使用索引和優化查詢。通過這些步驟，你將全面掌握MySQL的使用和優化。
現實世界Mysql：示例和用例Apr 14, 2025 am 12:15 AMMySQL在現實世界的應用包括基礎數據庫設計和復雜查詢優化。 1)基本用法：用於存儲和管理用戶數據，如插入、查詢、更新和刪除用戶信息。 2)高級用法：處理複雜業務邏輯，如電子商務平台的訂單和庫存管理。 3)性能優化：通過合理使用索引、分區表和查詢緩存來提升性能。
MySQL中的SQL命令：實踐示例Apr 14, 2025 am 12:09 AMMySQL中的SQL命令可以分為DDL、DML、DQL、DCL等類別，用於創建、修改、刪除數據庫和表，插入、更新、刪除數據，以及執行複雜的查詢操作。 1.基本用法包括CREATETABLE創建表、INSERTINTO插入數據和SELECT查詢數據。 2.高級用法涉及JOIN進行表聯接、子查詢和GROUPBY進行數據聚合。 3.常見錯誤如語法錯誤、數據類型不匹配和權限問題可以通過語法檢查、數據類型轉換和權限管理來調試。 4.性能優化建議包括使用索引、避免全表掃描、優化JOIN操作和使用事務來保證數據一致性
InnoDB如何處理酸合規性？Apr 14, 2025 am 12:03 AMInnoDB通過undolog實現原子性，通過鎖機制和MVCC實現一致性和隔離性，通過redolog實現持久性。 1）原子性：使用undolog記錄原始數據，確保事務可回滾。 2）一致性：通過行級鎖和MVCC確保數據一致。 3）隔離性：支持多種隔離級別，默認使用REPEATABLEREAD。 4）持久性：使用redolog記錄修改，確保數據持久保存。
MySQL的位置：數據庫和編程Apr 13, 2025 am 12:18 AMMySQL在數據庫和編程中的地位非常重要，它是一個開源的關係型數據庫管理系統，廣泛應用於各種應用場景。 1）MySQL提供高效的數據存儲、組織和檢索功能，支持Web、移動和企業級系統。 2）它使用客戶端-服務器架構，支持多種存儲引擎和索引優化。 3）基本用法包括創建表和插入數據，高級用法涉及多表JOIN和復雜查詢。 4）常見問題如SQL語法錯誤和性能問題可以通過EXPLAIN命令和慢查詢日誌調試。 5）性能優化方法包括合理使用索引、優化查詢和使用緩存，最佳實踐包括使用事務和PreparedStatemen
MySQL：從小型企業到大型企業Apr 13, 2025 am 12:17 AMMySQL適合小型和大型企業。 1)小型企業可使用MySQL進行基本數據管理，如存儲客戶信息。 2)大型企業可利用MySQL處理海量數據和復雜業務邏輯，優化查詢性能和事務處理。
幻影是什麼讀取的，InnoDB如何阻止它們（下一個鍵鎖定）？Apr 13, 2025 am 12:16 AMInnoDB通過Next-KeyLocking機制有效防止幻讀。 1）Next-KeyLocking結合行鎖和間隙鎖，鎖定記錄及其間隙，防止新記錄插入。 2）在實際應用中，通過優化查詢和調整隔離級別，可以減少鎖競爭，提高並發性能。
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