select file_name ,tablespace_name from dba_data_files ;
FILE_NAME TABLESPACE_NAME
--------------------------------------------- ------------------------------
+DATA/rac/datafile/system.259.926647219 SYSTEM
+DATA/rac/datafile/sysaux.260.926647323 SYSAUX
+DATA/rac/datafile/undotbs1.261.926647405 UNDOTBS1
+DATA/rac/datafile/undotbs2.263.926647467 UNDOTBS2
+DATA/rac/datafile/users.264.926647499 USERS
+DATA/rac/datafile/admin_tbs.274.927927081 ADMIN_TBS
+DATA/rac/datafile/admin_tb2.275.927927171 ADMIN_TB2
+DATA/rac/datafile/tbs_low_freq.276.927939255 TBS_LOW_FREQ
/oracle/app/oracle/11.2/db_1/dbs/q1_orders Q1_ORDERS
/oracle/app/oracle/11.2/db_1/dbs/q2_orders Q2_ORDERS
/oracle/app/oracle/11.2/db_1/dbs/q3_orders Q3_ORDERS
/oracle/app/oracle/11.2/db_1/dbs/q4_orders Q4_ORDERS
/oracle/app/oracle/11.2/db_1/dbs/2006_orders 2006_ORDERS
/oracle/app/oracle/11.2/db_1/dbs/2005_orders 2005_ORDERS
/oracle/app/oracle/11.2/db_1/dbs/2004_orders 2004_ORDERS
/oracle/app/oracle/11.2/db_1/dbs/old_orders OLD_ORDERS
/oracle/app/oracle/11.2/db_1/dbs/cc_this_mont CC_THIS_MONTH
数据文件都节点1本地。
案例重演：
sys@RAC> show parameter db_create_file_dest
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
db_create_file_dest string +DATA
采用了omf管理
sys@RAC> create tablespace qn datafile size 20m ;
Tablespace created.
sys@RAC> select file_name ,tablespace_name from dba_data_files ;
FILE_NAME TABLESPACE_NAME
--------------------------------------------- ------------------------------
.........
+DATA/rac/datafile/qn.277.928807173 QN
此时发现数据文件qn建在ASM存储上
sys@RAC> create tablespace qn2 datafile 'qn2' size 20m ;
Tablespace created.
sys@RAC> select file_name ,tablespace_name from dba_data_files ;
FILE_NAME TABLESPACE_NAME
--------------------------------------------- ------------------------------
/oracle/app/oracle/11.2/db_1/dbs/cc_prev_12 CC_PREV_12MTH
/oracle/app/oracle/11.2/db_1/dbs/cc_old_tran CC_OLD_TRAN
+DATA/rac/datafile/qn.277.928807173 QN
/oracle/app/oracle/11.2/db_1/dbs/qn2 QN2
此时发现数据文件qn2建在系统文件上,这样会出问题的，其节点报错。
那么如何把这个数据库的系统文件迁移到ASM上呢？
在线迁移数据文件至ASM上：
1. offline数据文件
select file_name ,tablespace_name from dba_data_files where tablespace_name in ('Q1_ORDERS','Q2_ORDERS','Q3_ORDERS','Q4_ORDERS','2006_ORDERS','2005_ORDERS','2004_ORDERS','OLD_ORDERS','CC_THIS_MONTH','CC_PREV_MONTH','CC_PREV_12MTH','QN2' ) ;
FILE_NAME TABLESPACE_NAME
------------------------------------------------------------ ------------------------------
/oracle/app/oracle/11.2/db_1/dbs/q1_orders Q1_ORDERS
/oracle/app/oracle/11.2/db_1/dbs/q2_orders Q2_ORDERS
/oracle/app/oracle/11.2/db_1/dbs/q3_orders Q3_ORDERS
/oracle/app/oracle/11.2/db_1/dbs/q4_orders Q4_ORDERS
/oracle/app/oracle/11.2/db_1/dbs/2006_orders 2006_ORDERS
/oracle/app/oracle/11.2/db_1/dbs/2005_orders 2005_ORDERS
/oracle/app/oracle/11.2/db_1/dbs/2004_orders 2004_ORDERS
/oracle/app/oracle/11.2/db_1/dbs/old_orders OLD_ORDERS
/oracle/app/oracle/11.2/db_1/dbs/cc_this_month CC_THIS_MONTH
/oracle/app/oracle/11.2/db_1/dbs/cc_prev_month CC_PREV_MONTH
/oracle/app/oracle/11.2/db_1/dbs/cc_prev_12 CC_PREV_12MTH
/oracle/app/oracle/11.2/db_1/dbs/qn2 QN2
2. rman copy
alter tablespace Q1_ORDERS offline ;
backup as copy datafile '/oracle/app/oracle/11.2/db_1/dbs/q1_orders' format '+DATA';
or
copy datafile '/oracle/app/oracle/11.2/db_1/dbs/q1_orders' to '+DATA';
RMAN> copy datafile '/oracle/app/oracle/11.2/db_1/dbs/q1_orders' to '+DATA';
Starting backup at 2016-11-25 02:55:42
using target database control file instead of recovery catalog
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=28 instance=rac1 device type=DISK
channel ORA_DISK_1: starting datafile copy
input datafile file number=00009 name=/oracle/app/oracle/11.2/db_1/dbs/q1_orders
output file name=+DATA/rac/datafile/q1_orders.278.928810547 tag=TAG20161125T025546 RECID=1 STAMP=928810550
channel ORA_DISK_1: datafile copy complete, elapsed time: 00:00:03
Finished backup at 2016-11-25 02:55:50
3. rename
alter database rename file 'D:\NSOADP\SYSTEM01.DBF' to '+ORADATA/nsoa/datafile/system.260.877082571';
or
switch datafile 37 to copy;
RMAN> switch datafile '/oracle/app/oracle/11.2/db_1/dbs/q1_orders' to copy ;
datafile 9 switched to datafile copy "+DATA/rac/datafile/q1_orders.278.928810547"
4. recover
recover datafile '+DATA/rac/datafile/q1_orders.278.928810547';
5. online
alter tablespace Q1_ORDERS online
sys@RAC> select file_name ,tablespace_name from dba_data_files where tablespace_name in ('Q1_ORDERS')
2 /
FILE_NAME TABLESPACE_NAME
------------------------------------------------------------ ------------------------------
+DATA/rac/datafile/q1_orders.278.928810547 Q1_ORDERS
快速恢复:
sys@RAC> select file_name ,tablespace_name from dba_data_files where tablespace_name in ('Q2_ORDERS','Q3_ORDERS','Q4_ORDERS','2006_ORDERS','2005_ORDERS','2004_ORDERS','OLD_ORDERS','CC_THIS_MONTH','CC_PREV_MONTH','CC_PREV_12MTH','QN2' ) ;
FILE_NAME TABLESPACE_NAME
------------------------------------------------------------ ------------------------------
/oracle/app/oracle/11.2/db_1/dbs/q2_orders Q2_ORDERS
/oracle/app/oracle/11.2/db_1/dbs/q3_orders Q3_ORDERS
/oracle/app/oracle/11.2/db_1/dbs/q4_orders Q4_ORDERS
/oracle/app/oracle/11.2/db_1/dbs/2006_orders 2006_ORDERS
/oracle/app/oracle/11.2/db_1/dbs/2005_orders 2005_ORDERS
/oracle/app/oracle/11.2/db_1/dbs/2004_orders 2004_ORDERS
/oracle/app/oracle/11.2/db_1/dbs/old_orders OLD_ORDERS
/oracle/app/oracle/11.2/db_1/dbs/cc_this_month CC_THIS_MONTH
/oracle/app/oracle/11.2/db_1/dbs/cc_prev_month CC_PREV_MONTH
/oracle/app/oracle/11.2/db_1/dbs/cc_prev_12 CC_PREV_12MTH
/oracle/app/oracle/11.2/db_1/dbs/qn2 QN2
sys@RAC> select 'alter tablespace '|| tablespace_name||' offline;' from dba_data_files where tablespace_name in ('Q2_ORDERS','Q3_ORDERS','Q4_ORDERS','2006_ORDERS','2005_ORDERS','2004_ORDERS','OLD_ORDERS','CC_THIS_MONTH','CC_PREV_MONTH','CC_PREV_12MTH','QN2'
) ;
'ALTERTABLESPACE'||TABLESPACE_NAME||'OFFLINE;'
--------------------------------------------------------
alter tablespace Q2_ORDERS offline;
alter tablespace Q3_ORDERS offline;
alter tablespace Q4_ORDERS offline;
alter tablespace 2006_ORDERS offline;
alter tablespace 2005_ORDERS offline;
alter tablespace 2004_ORDERS offline;
alter tablespace OLD_ORDERS offline;
alter tablespace CC_THIS_MONTH offline;
alter tablespace CC_PREV_MONTH offline;
alter tablespace CC_PREV_12MTH offline;
alter tablespace QN2 offline;
sys@RAC> sys@RAC> alter tablespace Q2_ORDERS offline;
alter tablespace Q3_ORDERS offline;
alter tablespace Q4_ORDERS offline;
alter tablespace 2006_ORDERS offline;
alter tablespace 2005_ORDERS offline;
alter tablespace 2004_ORDERS offline;
alter tablespace OLD_ORDERS offline;
alter tablespace CC_THIS_MONTH offline;
alter tablespace CC_PREV_MONTH offline;
alter tablespace CC_PREV_12MTH offline;
alter tablespace QN2 offline;
sys@RAC> alter tablespace "2006_ORDERS" offline
*
ERROR at line 1:
ORA-02140: invalid tablespace name
sys@RAC> alter tablespace 2005_ORDERS offline
*
ERROR at line 1:
ORA-02140: invalid tablespace name
sys@RAC> alter tablespace 2004_ORDERS offline
*
ERROR at line 1:
ORA-02140: invalid tablespace name
alter tablespace "2004_ORDERS" offline;
alter tablespace "2005_ORDERS" offline;
alter tablespace "2006_ORDERS" offline;
select 'copy datafile '''||file_name||''' to ''+DATA'';' from dba_data_files where tablespace_name in ('Q2_ORDERS','Q3_ORDERS','Q4_ORDERS','2006_ORDERS','2005_ORDERS','2004_ORDERS','OLD_ORDERS','CC_THIS_MONTH','CC_PREV_MONTH','CC_PREV_12MTH','QN2' ) ;
'COPYDATAFILE'''||FILE_NAME||'''TO''+DATA'';'
----------------------------------------------------------------------------------------------------------------------------------------------------------
copy datafile '/oracle/app/oracle/11.2/db_1/dbs/q2_orders' to '+DATA';
copy datafile '/oracle/app/oracle/11.2/db_1/dbs/q3_orders' to '+DATA';
copy datafile '/oracle/app/oracle/11.2/db_1/dbs/q4_orders' to '+DATA';
copy datafile '/oracle/app/oracle/11.2/db_1/dbs/2006_orders' to '+DATA';
copy datafile '/oracle/app/oracle/11.2/db_1/dbs/2005_orders' to '+DATA';
copy datafile '/oracle/app/oracle/11.2/db_1/dbs/2004_orders' to '+DATA';
copy datafile '/oracle/app/oracle/11.2/db_1/dbs/old_orders' to '+DATA';
copy datafile '/oracle/app/oracle/11.2/db_1/dbs/cc_this_month' to '+DATA';
copy datafile '/oracle/app/oracle/11.2/db_1/dbs/cc_prev_month' to '+DATA';
copy datafile '/oracle/app/oracle/11.2/db_1/dbs/cc_prev_12' to '+DATA';
copy datafile '/oracle/app/oracle/11.2/db_1/dbs/qn2' to '+DATA';
RMAN> copy datafile '/oracle/app/oracle/11.2/db_1/dbs/q2_orders' to '+DATA';
copy datafile '/oracle/app/oracle/11.2/db_1/dbs/q3_orders' to '+DATA';
copy datafile '/oracle/app/oracle/11.2/db_1/dbs/q4_orders' to '+DATA';
copy datafile '/oracle/app/oracle/11.2/db_1
/dbs/2006_orders' to '+DATA';
copy datafile '/oracle/app/oracle/11.2/db_1/dbs/2005_orders' to '+DATA';
copy datafile '/oracle/app/oracle/11.2/db_1/dbs/2004_orders' to '+DATA';
copy datafile '/oracle/app/oracle/11.2/db_1/dbs/old_orders' to '+DATA';
copy datafile '/oracle/app/oracle/11.2/db_1/dbs/cc_this_month' to '+DATA';
copy datafile '/oracle/app/oracle/11.2/db_1/dbs/cc_prev_month' to '+DATA';
copy datafile '/oracle/app/oracle/11.2/db_1/dbs/cc_prev_12' to '+DATA';
copy datafile '/oracle/app/oracle/11.2/db_1/dbs/qn2' to '+DATA';Starting backup at 2016-11-25 03:20:57
using channel ORA_DISK_1
channel ORA_DISK_1: starting datafile copy
input datafile file number=00010 name=/oracle/app/oracle/11.2/db_1/dbs/q2_orders
output file name=+DATA/rac/datafile/q2_orders.279.928812061 tag=TAG20161125T032059 RECID=3 STAMP=928812062
channel ORA_DISK_1: datafile copy complete, elapsed time: 00:00:03
Finished backup at 2016-11-25 03:21:02
RMAN>
Starting backup at 2016-11-25 03:21:08
using channel ORA_DISK_1
channel ORA_DISK_1: starting datafile copy
input datafile file number=00011 name=/oracle/app/oracle/11.2/db_1/dbs/q3_orders
output file name=+DATA/rac/datafile/q3_orders.280.928812071 tag=TAG20161125T032109 RECID=4 STAMP=928812073
channel ORA_DISK_1: datafile copy complete, elapsed time: 00:00:07
Finished backup at 2016-11-25 03:21:17
RMAN>
Starting backup at 2016-11-25 03:21:22
using channel ORA_DISK_1
channel ORA_DISK_1: starting datafile copy
input datafile file number=00012 name=/oracle/app/oracle/11.2/db_1/dbs/q4_orders
output file name=+DATA/rac/datafile/q4_orders.281.928812085 tag=TAG20161125T032124 RECID=5 STAMP=928812088
channel ORA_DISK_1: datafile copy complete, elapsed time: 00:00:03
Finished backup at 2016-11-25 03:21:28
RMAN>
Starting backup at 2016-11-25 03:21:33
using channel ORA_DISK_1
channel ORA_DISK_1: starting datafile copy
input datafile file number=00013 name=/oracle/app/oracle/11.2/db_1/dbs/2006_orders
output file name=+DATA/rac/datafile/2006_orders.282.928812095 tag=TAG20161125T032134 RECID=6 STAMP=928812099
channel ORA_DISK_1: datafile copy complete, elapsed time: 00:00:07
Finished backup at 2016-11-25 03:21:42
RMAN>
Starting backup at 2016-11-25 03:21:46
using channel ORA_DISK_1
channel ORA_DISK_1: starting datafile copy
input datafile file number=00014 name=/oracle/app/oracle/11.2/db_1/dbs/2005_orders
output file name=+DATA/rac/datafile/2005_orders.283.928812109 tag=TAG20161125T032148 RECID=7 STAMP=928812112
channel ORA_DISK_1: datafile copy complete, elapsed time: 00:00:07
Finished backup at 2016-11-25 03:21:56
RMAN>
Starting backup at 2016-11-25 03:22:00
using channel ORA_DISK_1
channel ORA_DISK_1: starting datafile copy
input datafile file number=00015 name=/oracle/app/oracle/11.2/db_1/dbs/2004_orders
output file name=+DATA/rac/datafile/2004_orders.284.928812123 tag=TAG20161125T032202 RECID=8 STAMP=928812126
channel ORA_DISK_1: datafile copy complete, elapsed time: 00:00:07
Finished backup at 2016-11-25 03:22:10
RMAN>
Starting backup at 2016-11-25 03:22:14
using channel ORA_DISK_1
channel ORA_DISK_1: starting datafile copy
input datafile file number=00016 name=/oracle/app/oracle/11.2/db_1/dbs/old_orders
output file name=+DATA/rac/datafile/old_orders.285.928812137 tag=TAG20161125T032216 RECID=9 STAMP=928812141
channel ORA_DISK_1: datafile copy complete, elapsed time: 00:00:07
Finished backup at 2016-11-25 03:22:24
RMAN>
Starting backup at 2016-11-25 03:22:29
using channel ORA_DISK_1
channel ORA_DISK_1: starting datafile copy
input datafile file number=00017 name=/oracle/app/oracle/11.2/db_1/dbs/cc_this_month
output file name=+DATA/rac/datafile/cc_this_month.286.928812151 tag=TAG20161125T032231 RECID=10 STAMP=928812154
channel ORA_DISK_1: datafile copy complete, elapsed time: 00:00:03
Finished backup at 2016-11-25 03:22:34
RMAN>
Starting backup at 2016-11-25 03:22:45
using channel ORA_DISK_1
channel ORA_DISK_1: starting datafile copy
input datafile file number=00018 name=/oracle/app/oracle/11.2/db_1/dbs/cc_prev_month
output file name=+DATA/rac/datafile/cc_prev_month.287.928812167 tag=TAG20161125T032246 RECID=11 STAMP=928812167
channel ORA_DISK_1: datafile copy complete, elapsed time: 00:00:01
Finished backup at 2016-11-25 03:22:47
RMAN>
Starting backup at 2016-11-25 03:22:52
using channel ORA_DISK_1
channel ORA_DISK_1: starting datafile copy
input datafile file number=00019 name=/oracle/app/oracle/11.2/db_1/dbs/cc_prev_12
output file name=+DATA/rac/datafile/cc_prev_12mth.288.928812175 tag=TAG20161125T032253 RECID=12 STAMP=928812175
channel ORA_DISK_1: datafile copy complete, elapsed time: 00:00:03
Finished backup at 2016-11-25 03:22:57
Starting backup at 2016-11-25 03:26:09
RMAN>
using channel ORA_DISK_1
channel ORA_DISK_1: starting datafile copy
input datafile file number=00022 name=/oracle/app/oracle/11.2/db_1/dbs/qn2
output file name=+DATA/rac/datafile/qn2.289.928812371 tag=TAG20161125T032611 RECID=13 STAMP=928812376
channel ORA_DISK_1: datafile copy complete, elapsed time: 00:00:07
Finished backup at 2016-11-25 03:26:18
sys@RAC> select 'switch datafile '''||file_name||''' to copy;' from dba_data_files where tablespace_name in ('Q2_ORDERS','Q3_ORDERS','Q4_ORDERS','2006_ORDERS','2005_ORDERS','2004_ORDERS','OLD_ORDERS','CC_THIS_MONTH','CC_PREV_MONTH','CC_PREV_12MTH','QN2'
) ;
'SWITCHDATAFILE'''||FILE_NAME||'''TOCOPY;'
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
switch datafile '/oracle/app/oracle/11.2/db_1/dbs/q2_orders' to copy;
switch datafile '/oracle/app/oracle/11.2/db_1/dbs/q3_orders' to copy;
switch datafile '/oracle/app/oracle/11.2/db_1/dbs/q4_orders' to copy;
switch datafile '/oracle/app/oracle/11.2/db_1/dbs/2006_orders' to copy;
switch datafile '/oracle/app/oracle/11.2/db_1/dbs/2005_orders' to copy;
switch datafile '/oracle/app/oracle/11.2/db_1/dbs/2004_orders' to copy;
switch datafile '/oracle/app/oracle/11.2/db_1/dbs/old_orders' to copy;
switch datafile '/oracle/app/oracle/11.2/db_1/dbs/cc_this_month' to copy;
switch datafile '/oracle/app/oracle/11.2/db_1/dbs/cc_prev_month' to copy;
switch datafile '/oracle/app/oracle/11.2/db_1/dbs/cc_prev_12' to copy;
switch datafile '/oracle/app/oracle/11.2/db_1/dbs/qn2' to copy;
RMAN> switch datafile '/oracle/app/oracle/11.2/db_1/dbs/q2_orders' to copy;
switch datafile '/oracle/app/oracle/11.2/db_1/dbs/q3_orders' to copy;
switch datafile '/oracle/app/oracle/11.2/db_1/dbs/q4_orders' to copy;
switch datafile '/oracle/app/oracle/11.2/db_1/
dbs/2006_orders' to copy;
switch datafile '/oracle/app/oracle/11.2/db_1/dbs/2005_orders' to copy;
switch datafile '/oracle/app/oracle/11.2/db_1/dbs/2004_orders' to copy;
switch datafile '/oracle/app/oracle/11.2/db_1/dbs/old_orders' to copy;
switch datafile '/oracle/app/oracle/11.2/db_1/dbs/cc_this_month' to copy;
switch datafile '/oracle/app/oracle/11.2/db_1/dbs/cc_prev_month' to copy;
switch datafile '/oracle/app/oracle/11.2/db_1/dbs/cc_prev_12' to copy;
switch datafile '/oracle/app/oracle/11.2/db_1/dbs/qn2' to copy;
datafile 10 switched to datafile copy "+DATA/rac/datafile/q2_orders.279.928812061"
RMAN>
datafile 11 switched to datafile copy "+DATA/rac/datafile/q3_orders.280.928812071"
RMAN>
datafile 12 switched to datafile copy "+DATA/rac/datafile/q4_orders.281.928812085"
RMAN>
datafile 13 switched to datafile copy "+DATA/rac/datafile/2006_orders.282.928812095"
RMAN>
datafile 14 switched to datafile copy "+DATA/rac/datafile/2005_orders.283.928812109"
RMAN>
datafile 15 switched to datafile copy "+DATA/rac/datafile/2004_orders.284.928812123"
RMAN>
datafile 16 switched to datafile copy "+DATA/rac/datafile/old_orders.285.928812137"
RMAN>
datafile 17 switched to datafile copy "+DATA/rac/datafile/cc_this_month.286.928812151"
RMAN>
datafile 18 switched to datafile copy "+DATA/rac/datafile/cc_prev_month.287.928812167"
RMAN>
datafile 19 switched to datafile copy "+DATA/rac/datafile/cc_prev_12mth.288.928812175"
RMAN>
datafile 22 switched to datafile copy "+DATA/rac/datafile/qn2.289.928812371"
alter tablespace Q3_ORDERS online;
alter tablespace Q4_ORDERS online;
alter tablespace "2006_ORDERS" online;
alter tablespace "2005_ORDERS" online;
alter tablespace "2004_ORDERS" online;
alter tablespace OLD_ORDERS online;
alter tablespace CC_THIS_MONTH online;
alter tablespace CC_PREV_MONTH online;
alter tablespace CC_PREV_12MTH online;
alter tablespace QN2 online;
sys@RAC> select file_name ,tablespace_name from dba_data_files where tablespace_name in ('Q1_ORDERS','Q2_ORDERS','Q3_ORDERS','Q4_ORDERS','2006_ORDERS','2005_ORDERS','2004_ORDERS','OLD_ORDERS','CC_THIS_MONTH','CC_PREV_MONTH','CC_PREV_12MTH','QN2' ) ;
FILE_NAME TABLESPACE_NAME
------------------------------------------------------------ ------------------------------
+DATA/rac/datafile/q1_orders.278.928810547 Q1_ORDERS
+DATA/rac/datafile/q2_orders.279.928812061 Q2_ORDERS
+DATA/rac/datafile/q3_orders.280.928812071 Q3_ORDERS
+DATA/rac/datafile/q4_orders.281.928812085 Q4_ORDERS
+DATA/rac/datafile/2006_orders.282.928812095 2006_ORDERS
+DATA/rac/datafile/2005_orders.283.928812109 2005_ORDERS
+DATA/rac/datafile/2004_orders.284.928812123 2004_ORDERS
+DATA/rac/datafile/old_orders.285.928812137 OLD_ORDERS
+DATA/rac/datafile/cc_this_month.286.928812151 CC_THIS_MONTH
+DATA/rac/datafile/cc_prev_month.287.928812167 CC_PREV_MONTH
+DATA/rac/datafile/cc_prev_12mth.288.928812175 CC_PREV_12MTH
+DATA/rac/datafile/qn2.289.928812371 QN2
至此系统上的数据文件都迁移到asm上。
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mySQL添加用戶：語法，選項和安全性最佳實踐May 13, 2025 am 12:12 AMtoaddauserinmysql，使用：createUser'username'@'host'Indessify'password'; there'showtodoitsecurely：1）choosethehostcarecarefullytocon trolaccess.2）setResourcelimitswithoptionslikemax_queries_per_hour.3）usestrong，iniquepasswords.4）Enforcessl/tlsconnectionswith
MySQL：如何避免字符串數據類型常見錯誤？May 13, 2025 am 12:09 AMtoAvoidCommonMistakeswithStringDatatatPesInMysQl，CloseStringTypenuances，chosethirtightType，andManageEngencodingAndCollationsEttingSefectery.1）usecharforfixed lengengtrings，varchar forvariable-varchar forbariaible length，andtext/blobforlargerdataa.2 seterters seterters seterters
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