RMAN恢复案例之--不完全恢复错误案例 RMAN恢复案例： 不完全恢复，由于在先前的数据文件备份有误，导致恢复失败。 [oracle@rh6~]$rmantarget/RecoveryManager:Release11.2.0.1.0-ProductiononSatSep2015:54:252014Copyright(c)1982,2009,Oracleand/oritsaffi
RMAN恢复案例之--不完全恢复错误案例
RMAN恢复案例：
不完全恢复，由于在先前的数据文件备份有误，导致恢复失败。
[oracle@rh6 ~]$ rman target /
Recovery Manager: Release 11.2.0.1.0 - Production on Sat Sep 20 15:54:25 2014
Copyright (c) 1982, 2009, Oracle and/or its affiliates. All rights reserved.
connected to target database: TEST1 (DBID=1195893416)
RMAN> run {
2> shutdown immediate;
3> startup mount;
4> set until time '2014-09-20 15:49:36';
5> restore database;
6> recover database ;
7> alter database open resetlogs;
8> sql'alter system switch logfile';
9> }
using target database control file instead of recovery catalog
database closed
database dismounted
Oracle instance shut down
connected to target database (not started)
Oracle instance started
database mounted
Total System Global Area 175767552 bytes
Fixed Size 1335276 bytes
Variable Size 142606356 bytes
Database Buffers 29360128 bytes
Redo Buffers 2465792 bytes
executing command: SET until clause
Starting restore at 20-SEP-14
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=18 device type=DISK
flashing back control file to SCN 9601534
channel ORA_DISK_1: starting datafile backup set restore
channel ORA_DISK_1: specifying datafile(s) to restore from backup set
channel ORA_DISK_1: restoring datafile 00002 to /u01/app/oracle/oradata/test1/sysaux01.dbf
channel ORA_DISK_1: restoring datafile 00004 to /u01/app/oracle/oradata/test1/users01.dbf
channel ORA_DISK_1: restoring datafile 00005 to /u01/app/oracle/oradata/test1/perfs.dbf
channel ORA_DISK_1: restoring datafile 00007 to /u01/app/oracle/oradata/test1/undotbs2.dbf
channel ORA_DISK_1: restoring datafile 00010 to /u01/app/oracle/oradata/test1/index01.dbf
channel ORA_DISK_1: reading from backup piece /dsk1/backup/test1/TEST1_240.bak
channel ORA_DISK_1: piece handle=/dsk1/backup/test1/TEST1_240.bak tag=TAG20140920T152720
channel ORA_DISK_1: restored backup piece 1
channel ORA_DISK_1: restore complete, elapsed time: 00:00:35
channel ORA_DISK_1: starting datafile backup set restore
channel ORA_DISK_1: specifying datafile(s) to restore from backup set
channel ORA_DISK_1: restoring datafile 00013 to /u01/app/oracle/oradata/test1/tbs_16.dbf
channel ORA_DISK_1: reading from backup piece /dsk1/backup/test1/TEST1_241.bak
channel ORA_DISK_1: piece handle=/dsk1/backup/test1/TEST1_241.bak tag=TAG20140920T152720
channel ORA_DISK_1: restored backup piece 1
channel ORA_DISK_1: restore complete, elapsed time: 00:00:01
channel ORA_DISK_1: starting datafile backup set restore
channel ORA_DISK_1: specifying datafile(s) to restore from backup set
channel ORA_DISK_1: restoring datafile 00001 to /u01/app/oracle/oradata/test1/system01.dbf
channel ORA_DISK_1: restoring datafile 00003 to /u01/app/oracle/oradata/test1/test1.dbf
channel ORA_DISK_1: restoring datafile 00006 to /u01/app/oracle/oradata/test1/dict1.dbf
channel ORA_DISK_1: reading from backup piece /dsk1/backup/test1/TEST1_239.bak
channel ORA_DISK_1: piece handle=/dsk1/backup/test1/TEST1_239.bak tag=TAG20140920T152720
channel ORA_DISK_1: restored backup piece 1
channel ORA_DISK_1: restore complete, elapsed time: 00:00:45
Finished restore at 20-SEP-14
Starting recover at 20-SEP-14
using channel ORA_DISK_1
starting media recoveryrecover 失败......
media recovery failed
RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-03002: failure of recover command at 09/20/2014 15:59:01
RMAN-20505: create datafile during recovery
RMAN-11003: failure during parse/execution of SQL statement: alter database recover if needed
start until time 'SEP 20 2014 15:49:36'
ORA-00283: recovery session canceled due to errors
ORA-01244: unnamed datafile(s) added to control file by media recovery
ORA-01110: data file 8: '/u01/app/oracle/oradata/test1/tbs2.dbf'
查看备份信息：
RMAN> list backup of database;
List of Backup Sets
===================
BS Key Type LV Size Device Type Elapsed Time Completion Time
------- ---- -- ---------- ----------- ------------ ---------------
229 Full 158.89M DISK 00:01:18 20-SEP-14
BP Key: 229 Status: AVAILABLE Compressed: NO Tag: TAG20140920T152720
Piece Name: /dsk1/backup/test1/TEST1_240.bak
List of Datafiles in backup set 229
File LV Type Ckp SCN Ckp Time Name
---- -- ---- ---------- --------- ----
2 Full 9601534 20-SEP-14 /u01/app/oracle/oradata/test1/sysaux01.dbf
4 Full 9601534 20-SEP-14 /u01/app/oracle/oradata/test1/users01.dbf
5 Full 9601534 20-SEP-14 /u01/app/oracle/oradata/test1/perfs.dbf
7 Full 9601534 20-SEP-14 /u01/app/oracle/oradata/test1/undotbs2.dbf
10 Full 9601534 20-SEP-14 /u01/app/oracle/oradata/test1/index01.dbf
BS Key Type LV Size Device Type Elapsed Time Completion Time
------- ---- -- ---------- ----------- ------------ ---------------
230 Full 1.06M DISK 00:00:01 20-SEP-14
BP Key: 230 Status: AVAILABLE Compressed: NO Tag: TAG20140920T152720
Piece Name: /dsk1/backup/test1/TEST1_241.bak
List of Datafiles in backup set 230
File LV Type Ckp SCN Ckp Time Name
---- -- ---- ---------- --------- ----
13 Full 9601534 20-SEP-14 /u01/app/oracle/oradata/test1/tbs_16.dbf
BS Key Type LV Size Device Type Elapsed Time Completion Time
------- ---- -- ---------- ----------- ------------ ---------------
231 Full 609.73M DISK 00:01:32 20-SEP-14
BP Key: 231 Status: AVAILABLE Compressed: NO Tag: TAG20140920T152720
Piece Name: /dsk1/backup/test1/TEST1_239.bak
List of Datafiles in backup set 231
File LV Type Ckp SCN Ckp Time Name
---- -- ---- ---------- --------- ----
1 Full 9601534 20-SEP-14 /u01/app/oracle/oradata/test1/system01.dbf
3 Full 9601534 20-SEP-14 /u01/app/oracle/oradata/test1/test1.dbf
6 Full 9601534 20-SEP-14 /u01/app/oracle/oradata/test1/dict1.dbf
8 Full 9601534 20-SEP-14 /u01/app/oracle/product/11.2.0/db_1/dbs/UNNAMED00008在备份中发现:
'/u01/app/oracle/product/11.2.0/db_1/dbs/UNNAMED00008',而在数据库中并没有这个数据文件！
解决方法：
将datafile offline，open数据库：
16:02:43 SYS@ test1 >alter database datafile 8 offline; Database altered.
recover database跳过此表空间：
RMAN> recover database skip tablespace tbs2;
Starting recover at 20-SEP-14 using channel ORA_DISK_1 Executing: alter database datafile 8 offline starting media recovery media recovery complete, elapsed time: 00:00:30 Finished recover at 20-SEP-14
查看告警日志：
alter database datafile 8 offline Completed: alter database datafile 8 offline alter database recover datafile list clear Completed: alter database recover datafile list clear alter database recover datafile list 1 , 2 , 3 , 4 , 5 , 6 , 7 , 10 , 13 Completed: alter database recover datafile list 1 , 2 , 3 , 4 , 5 , 6 , 7 , 10 , 13 alter database recover if needed start Media Recovery Start Serial Media Recovery started Recovery of Online Redo Log: Thread 1 Group 5 Seq 15 Reading mem 0 Mem# 0: /dsk1/oradata/test1/redo05a.log Sat Sep 20 16:06:51 2014 Media Recovery Complete (test1) Completed: alter database recover if needed start
打开数据库删除此表空间：
16:04:42 SYS@ test1 >conn /as sysdba; Connected. 16:10:10 SYS@ test1 >alter database open; Database altered. Elapsed: 00:00:21.63 16:10:54 SYS@ test1 >select name from v$datafile; NAME -------------------------------------------------- /u01/app/oracle/oradata/test1/system01.dbf /u01/app/oracle/oradata/test1/sysaux01.dbf /u01/app/oracle/oradata/test1/test1.dbf /u01/app/oracle/oradata/test1/users01.dbf /u01/app/oracle/oradata/test1/perfs.dbf /u01/app/oracle/oradata/test1/dict1.dbf /u01/app/oracle/oradata/test1/undotbs2.dbf /u01/app/oracle/product/11.2.0/db_1/dbs/UNNAMED000 08 /u01/app/oracle/oradata/test1/index01.dbf /u01/app/oracle/oradata/test1/tbs_16.dbf 10 rows selected. 16:11:10 SYS@ test1 >drop tablespace tbs2 including contents and datafiles; Tablespace dropped. 16:11:32 SYS@ test1 >select name from v$datafile; NAME -------------------------------------------------- /u01/app/oracle/oradata/test1/system01.dbf /u01/app/oracle/oradata/test1/sysaux01.dbf /u01/app/oracle/oradata/test1/test1.dbf /u01/app/oracle/oradata/test1/users01.dbf /u01/app/oracle/oradata/test1/perfs.dbf /u01/app/oracle/oradata/test1/dict1.dbf /u01/app/oracle/oradata/test1/undotbs2.dbf /u01/app/oracle/oradata/test1/index01.dbf /u01/app/oracle/oradata/test1/tbs_16.dbf 9 rows selected.
对数据库做重新做全备，再次做数据恢复！
恢复过程又出错：
RMAN> run {
2> shutdown immediate;
3> startup mount;
4> set until time '2014-09-20 16:19:30';
5> restore database;
6> recover database;
7> alter database open resetlogs;
8> }
database closed
database dismounted
Oracle instance shut down
connected to target database (not started)
Oracle instance started
database mounted
Total System Global Area 175767552 bytes
Fixed Size 1335276 bytes
Variable Size 142606356 bytes
Database Buffers 29360128 bytes
Redo Buffers 2465792 bytes
executing command: SET until clause
Starting restore at 20-SEP-14
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=18 device type=DISK
flashing back control file to SCN 9603237
RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-03002: failure of restore command at 09/20/2014 16:21:46
RMAN-06085: must use SET NEWNAME command to restore datafile /u01/app/oracle/product/11.2.0/db_1/dbs/UNNAMED00008查看备份信息：
RMAN> list backup;
List of Backup Sets
===================
BS Key Type LV Size Device Type Elapsed Time Completion Time
------- ---- -- ---------- ----------- ------------ ---------------
233 Full 164.45M DISK 00:01:04 20-SEP-14
BP Key: 233 Status: AVAILABLE Compressed: NO Tag: TAG20140920T161544
Piece Name: /dsk1/backup/test1/TEST1_244.bak
List of Datafiles in backup set 233
File LV Type Ckp SCN Ckp Time Name
---- -- ---- ---------- --------- ----
2 Full 9603220 20-SEP-14 /u01/app/oracle/oradata/test1/sysaux01.dbf
5 Full 9603220 20-SEP-14 /u01/app/oracle/oradata/test1/perfs.dbf
7 Full 9603220 20-SEP-14 /u01/app/oracle/oradata/test1/undotbs2.dbf
10 Full 9603220 20-SEP-14 /u01/app/oracle/oradata/test1/index01.dbf
BS Key Type LV Size Device Type Elapsed Time Completion Time
------- ---- -- ---------- ----------- ------------ ---------------
234 Full 1.06M DISK 00:00:02 20-SEP-14
BP Key: 234 Status: AVAILABLE Compressed: NO Tag: TAG20140920T161544
Piece Name: /dsk1/backup/test1/TEST1_245.bak
List of Datafiles in backup set 234
File LV Type Ckp SCN Ckp Time Name
---- -- ---- ---------- --------- ----
13 Full 9603220 20-SEP-14 /u01/app/oracle/oradata/test1/tbs_16.dbf
BS Key Type LV Size Device Type Elapsed Time Completion Time
------- ---- -- ---------- ----------- ------------ ---------------
235 Full 613.10M DISK 00:01:28 20-SEP-14
BP Key: 235 Status: AVAILABLE Compressed: NO Tag: TAG20140920T161544
Piece Name: /dsk1/backup/test1/TEST1_243.bak
List of Datafiles in backup set 235
File LV Type Ckp SCN Ckp Time Name
---- -- ---- ---------- --------- ----
1 Full 9603220 20-SEP-14 /u01/app/oracle/oradata/test1/system01.dbf
3 Full 9603220 20-SEP-14 /u01/app/oracle/oradata/test1/test1.dbf
4 Full 9603220 20-SEP-14 /u01/app/oracle/oradata/test1/users01.dbf
6 Full 9603220 20-SEP-14 /u01/app/oracle/oradata/test1/dict1.dbf
BS Key Type LV Size Device Type Elapsed Time Completion Time
------- ---- -- ---------- ----------- ------------ ---------------
236 Full 11.33M DISK 00:00:05 20-SEP-14
BP Key: 236 Status: AVAILABLE Compressed: NO Tag: TAG20140920T161714
Piece Name: /dsk4/backup/TEST1/autobackup/2014_09_20/o1_mf_s_858788041_b1tg0gds_.bkp
SPFILE Included: Modification time: 03-SEP-14
SPFILE db_unique_name: TEST1
Control File Included: Ckp SCN: 9603237 Ckp time: 20-SEP-14restore controlfile：
RMAN> list backup of controlfile;
List of Backup Sets
===================
BS Key Type LV Size Device Type Elapsed Time Completion Time
------- ---- -- ---------- ----------- ------------ ---------------
236 Full 11.33M DISK 00:00:05 20-SEP-14
BP Key: 236 Status: AVAILABLE Compressed: NO Tag: TAG20140920T161714
Piece Name: /dsk4/backup/TEST1/autobackup/2014_09_20/o1_mf_s_858788041_b1tg0gds_.bkp
Control File Included: Ckp SCN: 9603237 Ckp time: 20-SEP-14
RMAN> shutdown immediate;
database dismounted
Oracle instance shut down
RMAN> startup nomount;
connected to target database (not started)
Oracle instance started
Total System Global Area 175767552 bytes
Fixed Size 1335276 bytes
Variable Size 142606356 bytes
Database Buffers 29360128 bytes
Redo Buffers 2465792 bytes
RMAN> restore controlfile from autobackup;
Starting restore at 20-SEP-14
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=19 device type=DISK
recovery area destination: /dsk4/backup
database name (or database unique name) used for search: TEST1
channel ORA_DISK_1: AUTOBACKUP /dsk4/backup/TEST1/autobackup/2014_09_20/o1_mf_s_858788041_b1tg0gds_.bkp found in the recovery area
channel ORA_DISK_1: looking for AUTOBACKUP on day: 20140920
channel ORA_DISK_1: restoring control file from AUTOBACKUP /dsk4/backup/TEST1/autobackup/2014_09_20/o1_mf_s_858788041_b1tg0gds_.bkp
channel ORA_DISK_1: control file restore from AUTOBACKUP complete
output file name=/u01/app/oracle/oradata/test1/control01.ctl
output file name=/dsk1/oradata/test1/control02.ctl
output file name=/dsk2/oradata/test1/control03.ctl
Finished restore at 20-SEP-14重新做恢复：
RMAN> run {
2> shutdown immediate;
3> startup mount;
4> set until time '2014-09-20 16:19:30';
5> restore database;
6> recover database;
7> alter database open resetlogs;
8> }
Oracle instance shut down
connected to target database (not started)
Oracle instance started
database mounted
Total System Global Area 175767552 bytes
Fixed Size 1335276 bytes
Variable Size 142606356 bytes
Database Buffers 29360128 bytes
Redo Buffers 2465792 bytes
executing command: SET until clause
Starting restore at 20-SEP-14
Starting implicit crosscheck backup at 20-SEP-14
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=18 device type=DISK
Crosschecked 3 objects
Finished implicit crosscheck backup at 20-SEP-14
Starting implicit crosscheck copy at 20-SEP-14
using channel ORA_DISK_1
Finished implicit crosscheck copy at 20-SEP-14
searching for all files in the recovery area
cataloging files...
cataloging done
List of Cataloged Files
=======================
File Name: /dsk4/backup/TEST1/autobackup/2014_09_20/o1_mf_s_858788041_b1tg0gds_.bkp
File Name: /dsk4/backup/TEST1/autobackup/2014_09_14/o1_mf_s_858262943_b1bf156d_.bkp
File Name: /dsk4/backup/TEST1/autobackup/2014_09_14/o1_mf_s_858259416_b1b9lv2j_.bkp
File Name: /dsk4/backup/TEST1/autobackup/2014_09_14/o1_mf_s_858261087_b1bc76lg_.bkp
File Name: /dsk4/backup/TEST1/autobackup/2014_09_14/o1_mf_s_858260002_b1bb58sq_.bkp
File Name: /dsk4/backup/TEST1/autobackup/2013_11_10/o1_mf_s_831135549_97ycp30c_.bkp
File Name: /dsk4/backup/TEST1/autobackup/2013_11_10/o1_mf_s_831134795_97yc0vk0_.bkp
File Name: /dsk4/backup/TEST1/autobackup/2013_11_10/o1_mf_s_831136532_97ydnsbl_.bkp
File Name: /dsk4/backup/TEST1/autobackup/2013_11_10/o1_mf_s_831135962_97yd2z3r_.bkp
using channel ORA_DISK_1
channel ORA_DISK_1: starting datafile backup set restore
channel ORA_DISK_1: specifying datafile(s) to restore from backup set
channel ORA_DISK_1: restoring datafile 00002 to /u01/app/oracle/oradata/test1/sysaux01.dbf
channel ORA_DISK_1: restoring datafile 00005 to /u01/app/oracle/oradata/test1/perfs.dbf
channel ORA_DISK_1: restoring datafile 00007 to /u01/app/oracle/oradata/test1/undotbs2.dbf
channel ORA_DISK_1: restoring datafile 00010 to /u01/app/oracle/oradata/test1/index01.dbf
channel ORA_DISK_1: reading from backup piece /dsk1/backup/test1/TEST1_244.bak
channel ORA_DISK_1: piece handle=/dsk1/backup/test1/TEST1_244.bak tag=TAG20140920T161544
channel ORA_DISK_1: restored backup piece 1
channel ORA_DISK_1: restore complete, elapsed time: 00:00:25
channel ORA_DISK_1: starting datafile backup set restore
channel ORA_DISK_1: specifying datafile(s) to restore from backup set
channel ORA_DISK_1: restoring datafile 00013 to /u01/app/oracle/oradata/test1/tbs_16.dbf
channel ORA_DISK_1: reading from backup piece /dsk1/backup/test1/TEST1_245.bak
channel ORA_DISK_1: piece handle=/dsk1/backup/test1/TEST1_245.bak tag=TAG20140920T161544
channel ORA_DISK_1: restored backup piece 1
channel ORA_DISK_1: restore complete, elapsed time: 00:00:01
channel ORA_DISK_1: starting datafile backup set restore
channel ORA_DISK_1: specifying datafile(s) to restore from backup set
channel ORA_DISK_1: restoring datafile 00001 to /u01/app/oracle/oradata/test1/system01.dbf
channel ORA_DISK_1: restoring datafile 00003 to /u01/app/oracle/oradata/test1/test1.dbf
channel ORA_DISK_1: restoring datafile 00004 to /u01/app/oracle/oradata/test1/users01.dbf
channel ORA_DISK_1: restoring datafile 00006 to /u01/app/oracle/oradata/test1/dict1.dbf
channel ORA_DISK_1: reading from backup piece /dsk1/backup/test1/TEST1_243.bak
channel ORA_DISK_1: piece handle=/dsk1/backup/test1/TEST1_243.bak tag=TAG20140920T161544
channel ORA_DISK_1: restored backup piece 1
channel ORA_DISK_1: restore complete, elapsed time: 00:00:55
Finished restore at 20-SEP-14
Starting recover at 20-SEP-14
using channel ORA_DISK_1
starting media recovery
archived log for thread 1 with sequence 17 is already on disk as file /dsk1/oradata/test1/redo04a.log
archived log for thread 1 with sequence 18 is already on disk as file /dsk1/oradata/test1/redo05a.log
archived log file name=/dsk1/oradata/test1/redo04a.log thread=1 sequence=17
archived log file name=/dsk1/oradata/test1/redo05a.log thread=1 sequence=18
media recovery complete, elapsed time: 00:00:08
Finished recover at 20-SEP-14
Starting recover at 20-SEP-14
using channel ORA_DISK_1
starting media recovery
archived log for thread 1 with sequence 17 is already on disk as file /dsk1/oradata/test1/redo04a.log
archived log for thread 1 with sequence 18 is already on disk as file /dsk1/oradata/test1/redo05a.log
archived log file name=/dsk1/oradata/test1/redo04a.log thread=1 sequence=17
archived log file name=/dsk1/oradata/test1/redo05a.log thread=1 sequence=18
media recovery complete, elapsed time: 00:00:08
Finished recover at 20-SEP-14
database opened@至此，不完全恢复成功！
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Huraikan mekanisme penguncian InnoDB (kunci yang dikongsi, kunci eksklusif, kunci niat, kunci rekod, kunci jurang, kunci seterusnya).Apr 12, 2025 am 12:16 AMMekanisme kunci InnoDB termasuk kunci bersama, kunci eksklusif, kunci niat, kunci rekod, kunci jurang dan kunci utama seterusnya. 1. Kunci dikongsi membolehkan urus niaga membaca data tanpa menghalang urus niaga lain dari membaca. 2. Kunci eksklusif menghalang urus niaga lain daripada membaca dan mengubah suai data. 3. Niat Kunci mengoptimumkan kecekapan kunci. 4. Rekod Rekod Kunci Kunci Rekod. 5. Gap Lock Locks Index Rakaman Gap. 6. Kunci kunci seterusnya adalah gabungan kunci rekod dan kunci jurang untuk memastikan konsistensi data.
Apakah sebab -sebab biasa prestasi pertanyaan MySQL yang lemah?Apr 12, 2025 am 12:11 AMSebab -sebab utama prestasi pertanyaan MySQL yang lemah termasuk tidak menggunakan indeks, pemilihan pelan pelaksanaan yang salah oleh pengoptimasi pertanyaan, reka bentuk jadual yang tidak munasabah, jumlah data yang berlebihan dan persaingan kunci. 1. Tiada indeks menyebabkan pertanyaan perlahan, dan menambah indeks dapat meningkatkan prestasi dengan ketara. 2. Gunakan perintah Jelaskan untuk menganalisis pelan pertanyaan dan cari ralat pengoptimuman. 3. Membina semula struktur meja dan mengoptimumkan keadaan gabungan dapat meningkatkan masalah reka bentuk jadual. 4. Apabila jumlah data adalah besar, pembahagian dan strategi bahagian meja diterima pakai. 5. Dalam persekitaran konkurensi yang tinggi, mengoptimumkan urus niaga dan strategi mengunci dapat mengurangkan persaingan kunci.
Bilakah anda harus menggunakan indeks komposit berbanding indeks lajur tunggal?Apr 11, 2025 am 12:06 AMDalam pengoptimuman pangkalan data, strategi pengindeksan hendaklah dipilih mengikut keperluan pertanyaan: 1. Apabila pertanyaan melibatkan pelbagai lajur dan urutan syarat ditetapkan, gunakan indeks komposit; 2. Apabila pertanyaan melibatkan pelbagai lajur tetapi urutan syarat tidak ditetapkan, gunakan pelbagai indeks lajur tunggal. Indeks komposit sesuai untuk mengoptimumkan pertanyaan berbilang lajur, manakala indeks lajur tunggal sesuai untuk pertanyaan tunggal lajur.
Bagaimana untuk mengenal pasti dan mengoptimumkan pertanyaan perlahan di MySQL? (Log pertanyaan perlahan, prestasi_schema)Apr 10, 2025 am 09:36 AMUntuk mengoptimumkan pertanyaan perlahan MySQL, SlowQuerylog dan Performance_Schema perlu digunakan: 1. Dayakan SlowQueryLog dan tetapkan ambang untuk merakam pertanyaan perlahan; 2. Gunakan Performance_Schema untuk menganalisis butiran pelaksanaan pertanyaan, cari kesesakan prestasi dan mengoptimumkan.
MySQL dan SQL: Kemahiran Penting untuk PemajuApr 10, 2025 am 09:30 AMMySQL dan SQL adalah kemahiran penting untuk pemaju. 1.MYSQL adalah sistem pengurusan pangkalan data sumber terbuka, dan SQL adalah bahasa standard yang digunakan untuk mengurus dan mengendalikan pangkalan data. 2.MYSQL menyokong pelbagai enjin penyimpanan melalui penyimpanan data yang cekap dan fungsi pengambilan semula, dan SQL melengkapkan operasi data yang kompleks melalui pernyataan mudah. 3. Contoh penggunaan termasuk pertanyaan asas dan pertanyaan lanjutan, seperti penapisan dan penyortiran mengikut keadaan. 4. Kesilapan umum termasuk kesilapan sintaks dan isu -isu prestasi, yang boleh dioptimumkan dengan memeriksa penyataan SQL dan menggunakan perintah menjelaskan. 5. Teknik pengoptimuman prestasi termasuk menggunakan indeks, mengelakkan pengimbasan jadual penuh, mengoptimumkan operasi menyertai dan meningkatkan kebolehbacaan kod.
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