如题:
1.如何理解varchar2类型采用non-padded,而char采用Blank-Padded方式比较?
2.oracle中统计信息如何收集?
3.计算2的64次方结果不对,不知什么原因?
代码清单:2的64次方根
SQL> select power(2,64) from dual;
POWER(2,64)
-----------
1.844674407SQL> select power(64,2) value from dual;
VALUE
----------
40964.rowidtochar(将rowid数据类型转换为字符类型)和chartorowid(将字符数据类型转换为rowid类型)的使用场合
5.请教dump的用法SQL> select dump(sysdate) from dual;
DUMP(SYSDATE)
--------------------------------------------------------------------------------
Typ=13 Len=8: 218,7,5,5,10,48,25,0
期待大家的解答!
1.如何理解varchar2类型采用non-padded,而char采用Blank-Padded方式比较?
2.oracle中统计信息如何收集?
3.计算2的64次方结果不对,不知什么原因?
代码清单:2的64次方根
SQL> select power(2,64) from dual;
POWER(2,64)
-----------
1.844674407SQL> select power(64,2) value from dual;
VALUE
----------
40964.rowidtochar(将rowid数据类型转换为字符类型)和chartorowid(将字符数据类型转换为rowid类型)的使用场合
5.请教dump的用法SQL> select dump(sysdate) from dual;
DUMP(SYSDATE)
--------------------------------------------------------------------------------
Typ=13 Len=8: 218,7,5,5,10,48,25,0
期待大家的解答!
SQL> set numformat 999999999999999999999999999999999999999--输出前,先设置一个输出数字的格式
SQL> select power(2,64) from dual; POWER(2,64)
----------------------------------------
18446744073709551616
简单的说
{'a','a'} in
table a (a1 vc(20),a2 c(20))
select '1' from a where a1=a2 结果 no rows
a1='a' a2='a '
http://www.itpub.net/thread-1080616-1-1.html
2、http://www.cnblogs.com/rootq/archive/2010/02/04/1663622.html
3、结果没错,只不过显示不开
code:
select to_char(power(2,64)) from dual;
可看到 18446744073709551616
3:
SQL> select power(2,64) from dual;
POWER(2,64)
-----------
1.844674407
你的是列宽太短,长度增加下5.dump记录列在DATAFILE中的类型和信息
下面一段内容摘自Oracle® Database SQL Reference 10g Release 2 (10.2)PurposeROWIDTOCHAR converts a rowid value to VARCHAR2 datatype. The result of this conversion is always 18 characters long.ExamplesThe following example converts a rowid value in the employees table to a character value. (Results vary for each build of the sample database.)SELECT ROWID FROM employees
WHERE ROWIDTOCHAR(ROWID) LIKE '%JAAB%';ROWID
------------------
AAAFfIAAFAAAABSAAb大多数时候ORACLE会自动对其进行隐式转换的
SQL> select t3.*,rowid,rowidtochar(rowid) from t3;
ID NAME ROWID ROWIDTOCHAR(ROWID)
---------- -------------------- ------------------ ------------------
1 a AAASOZAAEAAAK1IAAA AAASOZAAEAAAK1IAAA
2 b AAASOZAAEAAAK1IAAB AAASOZAAEAAAK1IAAB
3 c AAASOZAAEAAAK1IAAC AAASOZAAEAAAK1IAAC
4 d AAASOZAAEAAAK1IAAD AAASOZAAEAAAK1IAAD
SQL> select * from t3 where rowid = chartorowid('AAASOZAAEAAAK1IAAA');
ID NAME
---------- --------------------
1 a
SQL> select * from t3 where rowid = 'AAASOZAAEAAAK1IAAA';
ID NAME
---------- --------------------
1 a