SQL select t.rowid,t.* from scott.test t; ROWID DEPTNO DNAME LOC ------------------ ---------- -------------- ------------- AAAPtpAAEAAAADbAAA 10 ACCOUNTING NEW YORK AAAPtpAAEAAAADbAAB 20 RESEARCH DALLAS AAAPtpAAEAAAADbAAC 30 SALES CHICAGO
SQL> select t.rowid,t.* from scott.test t;ROWID DEPTNO DNAME LOC
------------------ ---------- -------------- -------------
AAAPtpAAEAAAADbAAA 10 ACCOUNTING NEW YORK
AAAPtpAAEAAAADbAAB 20 RESEARCH DALLAS
AAAPtpAAEAAAADbAAC 30 SALES CHICAGO
AAAPtpAAEAAAADbAAD 40 OPERATIONS BOSTON
rowid(AAAPtpAAEAAAADbAAD)详解
AAAPtp --object#
AAE --file#
AAAADb --block#
AAD --row#
SQL> select rowid ,
2 substr(rowid,1,6) "OBJECT#",
3 substr(rowid,7,3) "FILE#",
4 substr(rowid,10,6) "BLOCK#",
5 substr(rowid,16,3) "ROW#"
6 from scott.test;
ROWID OBJECT# FILE# BLOCK# ROW#
------------------ ------------------------ ------------ ------------------------ ------------
AAAPtpAAEAAAADbAAA AAAPtp AAE AAAADb AAA
AAAPtpAAEAAAADbAAB AAAPtp AAE AAAADb AAB
AAAPtpAAEAAAADbAAC AAAPtp AAE AAAADb AAC
AAAPtpAAEAAAADbAAD AAAPtp AAE AAAADb AAD
转换 rowid 的 object#
SQL> select DBMS_ROWID.ROWID_OBJECT('AAAPtpAAEAAAADbAAD') from dual
2 union all
3 select object_id from dba_objects where object_name = 'TEST' AND owner='SCOTT';
DBMS_ROWID.ROWID_OBJECT('AAAPTPAAEAAAADBAAD')
---------------------------------------------
64361
64361
转换 rowid 的 file# (相对文件编号)
SQL> select DBMS_ROWID.ROWID_RELATIVE_FNO('AAAPtpAAEAAAADbAAD') from dual
2 union all
3 select a.file_id from dba_data_files a,dba_segments b where b.SEGMENT_NAME ='TEST' and b.owner='SCOTT' and a.tablespace_name=b.tablespace_name;
DBMS_ROWID.ROWID_RELATIVE_FNO('AAAPTPAAEAAAADBAAD')
---------------------------------------------------
4
4
转换 rowid 的 block#
SQL> select dbms_rowid.rowid_block_number('AAAPtpAAEAAAADbAAD') from dual;
DBMS_ROWID.ROWID_BLOCK_NUMBER('AAAPTPAAEAAAADBAAD')
---------------------------------------------------
219
转换 rowid 的 row#
SQL> select DBMS_ROWID.ROWID_ROW_NUMBER(rowid) from scott.test;
DBMS_ROWID.ROWID_ROW_NUMBER(ROWID)
----------------------------------
0
1
2
3
转换 rowid 的绝对文件编号
SQL> select DBMS_ROWID.ROWID_TO_ABSOLUTE_FNO('AAAPtpAAEAAAADbAAD','SCOTT','TEST') from scott.test;
DBMS_ROWID.ROWID_TO_ABSOLUTE_FNO('AAAPTPAAEAAAADBAAD','SCOTT','TEST')
---------------------------------------------------------------------
4
4
4
4
<p><span></span></p><p><span><span>作者:xiangsir</span></span></p><p><span></span></p><p><span><span>QQ:444367417</span></span></p><p><span><span>MSN:xiangsir@hotmail.com</span></span></p>

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chosecharforfixed-lengthdata,varcharforvariable-lengthdata,andtextforlargetextfield.1)chariseffity forconsistent-lengthdatalikecodes.2)varcharsuitsvariable-lengthdatalikenames,ballancingflexibilitibility andperformance.3)

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tostorestringsefliceflicyInmySql,ChooSetherightDataTypeBasedyOrneOrneEds:1)USEcharforFixed-LengthStstringStringStringSlikeCountryCodes.2)UseVarcharforvariable-lengtthslikenames.3)USETEXTCONTENT.3)

选择MySQL的BLOB和TEXT数据类型时,BLOB适合存储二进制数据,TEXT适合存储文本数据。1)BLOB适用于图片、音频等二进制数据,2)TEXT适用于文章、评论等文本数据,选择时需考虑数据性质和性能优化。

No,youshouldnotusetherootuserinMySQLforyourproduct.Instead,createspecificuserswithlimitedprivilegestoenhancesecurityandperformance:1)Createanewuserwithastrongpassword,2)Grantonlynecessarypermissionstothisuser,3)Regularlyreviewandupdateuserpermissions

mySqlStringDatatatPessHouldBechoseBeadeDataCharacteristicsAndUsecases:1)USECHARFORFIXED LENGTHSTRINGSTRINGSLIKECOUNTRYCODES.2)USEDES.2)usevarcharforvariable-lengtthstringstringstringstringstringstringstringslikenames.3)usebinaryorvarrinaryorvarinarydatalbonydatalgebgeenfopical.4)


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