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l S£ºselect abs(-1) value
l O£ºselect abs(-1) value from dual
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l S£ºselect ceiling(-001) value
l O£ºselect ceil(-001) value from dual
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l S£ºselect floor(-001) value
l O£ºselect floor(-001) value from dual
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l S£ºselect cast(-002 as int) value
l O£ºselect trunc(-002) value from dual
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l S£ºselect round(23456,4) value 23460
l O£ºselect round(23456,4) value from dual 2346
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l S£ºselect Exp(1) value l O£ºselect Exp(1) value from dual
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l S£ºselect log(7182818284590451) value
l O£ºselect ln(7182818284590451) value from dual;
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l S£ºselect log10(10) value
l O£ºselect log(10,10) value from dual;
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l S£ºselect SQUARE(4) value
l O£ºselect power(4,2) value from dual
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l O£ºselect SQRT(4) value from dual
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l S£ºselect power(3,4) value
l O£ºselect power(3,4) value from dual
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l S£ºselect rand() value
l O£ºselect sys.dbms_random.value(0,1) value from dual;
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l S£ºselect sign(-8) value -1
l O£ºselect sign(-8) value from dual -1
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1.ÀûÓÃÏÂÃæµÄ½Å±¾´´½¨BOOK£¬READER ºÍ BORROW ±í£¬²¢Íê³ÉºóÃæµÄÁªÏµ¡£
CREATE TABLE BOOK(
NO CHAR(8) PRIMARY KEY,
TITLE VARCHAR2(50) NOT NULL,
AUTHOR VARCHAR2(20) ,
PUBLISH VARCHAR2(20),
PUB_DA ......
select * from sys.smon_scn_time;
--scn Óëʱ¼äµÄ¶ÔÓ¦¹ØÏµ
ÿ¸ô5·ÖÖÓ£¬ÏµÍ³²úÉúÒ»´Îϵͳʱ¼ä±ê¼ÇÓëscnµÄÆ¥Åä²¢´æÈësys.smon_scn_time±í¡£
select * from student as of scn 592258
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insert into student select * from student a ......
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1.ΪÁ˲»´òÂÒÔÀ´µÄ±íµÄÊý¾Ý,ËùÒÔ±¸·ÝÔÀ´µÄÊý¾Ý.
create table emp2 as select * from emp
create table emp3 as select * from emp
create table dept2 as select * from dept
create table salgrade2 as select * from salgrade
2.²é¿´±íµÄÉè¼ÆÇé¿ö:desc dept2;±íʾ²é¿´±ídept2µÄÉè¼ÆÇé¿ö.
3.²åÈëÊý¾Ýµ ......
1. ASCII
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SQL> select ascii(A) A,ascii(a) a,ascii(0) zero,ascii( ) space from dual;
A A ZERO SPACE
--------- --------- --------- ---------
65 97 48 32
2. CHR
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SQL> select chr(54740) zhao,chr(65) chr65 from dual;
ZH ......
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