SQL> select substr('liuyuehui',3) as first_name from dual;
FIRST_NAME
 --------------
 uyuehuiSQL> select substr('liuyuehui',1) as first_name from dual;
FIRST_NAME
 ------------------
 liuyuehuiSQL> select substr('liuyuehui',0) as first_name from dual;
FIRST_NAME
 ------------------
 liuyuehuiSQL> select substr('liuyuehui',-3,3) from dual;
SUBSTR
 ------
 huiSQL> select substr('liuyuehui',length('liuyuehui')-5) as first_name from dual;
FIRST_NAME
 ------------
 yuehuiSQL> select substr('feng',lenth('feng')-1) from dual;
 select substr('feng',lenth('feng')-1) from dual
                      *
 第 1 行出现错误:
 ORA-00904: "LENTH": 标识符无效 SQL> select substr('feng',length('feng')-1) from dual;
SUBS
 ----
 ngSQL> select substr('liufeng',3,7) as firstname,substr('liufeng',-4,4) as secondn
 ame from dual;FIRSTNAME  SECONDNA
 ---------- --------
 ufeng      fengSQL> select substr('liufeng',0,3) as firstname,substr('liufeng',-4,4) as secondn
 ame from dual;FIRSTN SECONDNA
 ------ --------
 liu    fengSQL> select upper(substr('liufeng',0,3) ) as firstname,lower(substr('liuyuehui',
 3)) as secondname from dual;FIRSTN SECONDNAME
 ------ --------------
 LIU    uyuehuiSQL> select upper(substr('liufeng',0,3) ) as firstname,lower(substr('liuyuehui',
 4)) as secondname from dual;FIRSTN SECONDNAME
 ------ ------------
 LIU    yuehuiSQL> select instr('Hello World!','or') from dual;
INSTR('HELLOWORLD!','OR')
 -------------------------
                         8SQL> select trim('   hello   ') from dual;
TRIM('HELL
 ----------
 helloSQL> select trim('   hello   ') as hi from dual;
HI
 ----------
 helloSQL> select lpad('smith',10,'*') from dual;
LPAD('SMITH',10,'*')
 --------------------
 *****smithSQL> select lpad('smith',10,'*') as star_smith from dual;
STAR_SMITH
 --------------------
 *****smithSQL> select rpad('smith',10,'*') as star_smith from dual;
STAR_SMITH
 --------------------
 smith*****SQL> select rpad('smith',10,'*') as reft_star_smith,lpad('smith',10,'*') as righ
 t_star_smith from dual;REFT_STAR_SMITH      RIGHT_STAR_SMITH
 -------------------- --------------------
 smith*****           *****smithSQL> select substr(instr('testmyname','or'),-4,4) from dual;
S
 - SQL>
 SQL> select substr(instr('testmyname','or'),-4,4) from dual;S
 - SQL> select instr('testmyname','or') from dual;
INSTR('TESTMYNAME','OR')
 ------------------------
                        0SQL> select instr('test myname','or') from dual;
INSTR('TESTMYNAME','OR')
 ------------------------
                        0SQL> select rpad('smith',10,'月') as reft_star_smith,lpad('smith',10,'*') as rig
 ht_star_smith from dual;REFT_STAR_SMITH          RIGHT_STAR_SMITH
 ------------------------ --------------------
 smith月月                *****smithSQL> select rpad('smith',10,'月') as reft_star_smith,lpad('smith',10,'月') as ri
 ght_star_smith from dual;REFT_STAR_SMITH          RIGHT_STAR_SMITH
 ------------------------ ------------------------
 smith月月                 月月smithSQL> select next_day(sysdate,'星期一') from dual;
NEXT_DAY(SYSDA
 --------------
 19-1月 -15SQL> select next_day(sysdate,'星期天') from dual;
 select next_day(sysdate,'星期天') from dual
                         *
 第 1 行出现错误:
 ORA-01846: 周中的日无效 SQL> select next_day(sysdate,'星期日') from dual;
NEXT_DAY(SYSDA
 --------------
 18-1月 -15SQL> select last_day(sysdate) from dual;
LAST_DAY(SYSDA
 --------------
 31-1月 -15SQL> select add_months(sysdate,1) from dual;
ADD_MONTHS(SYS
 --------------
 14-2月 -15SQL> select add_months(sysdate,1) as next_month from dual;
NEXT_MONTH
 --------------
 14-2月 -15SQL> select to_char(sysdate,'yyyy') from dual;
TO_CHAR(
 --------
 2015SQL> select to_char(sysdate,'mmmm') from dual;
TO_CHAR(
 --------
 0101SQL> select to_char(sysdate,'mm') from dual;
TO_C
 ----
 01SQL> select to_char(sysdate,'mm-ss') from dual;
TO_CHAR(SY
 ----------
 01-52SQL> select to_char(sysdate,’D’) from dual;//返回星期
   2
 SQL> select to_char(sysdate,’D’) from dual;
 select to_char(sysdate,’D’) from dual
                        *
 第 1 行出现错误:
 ORA-01756: 引号内的字符串没有正确结束 SQL> select to_char(sysdate,'D') from dual;
TO
 --
 4SQL> Select to_date(„20090210‟,‟yyyyMMdd‟) from dual;
 Select to_date(?20090210?,?yyyyMMdd?) from dual
                *
 第 1 行出现错误:
 ORA-00911: 无效字符 SQL> Select to_date('20090210"‟,‟yyyyMMdd‟) from dual;
 ERROR:
 ORA-01756: 引号内的字符串没有正确结束 SQL> Select to_date('20090210'‟,‟yyyyMMdd‟) from dual;
 Select to_date('20090210'?,?yyyyMMdd?) from dual
                          *
 第 1 行出现错误:
 ORA-00911: 无效字符 SQL> Select to_date('20090210',yyyyMMdd‟) from dual;
 Select to_date('20090210',yyyyMMdd?) from dual
                                   *
 第 1 行出现错误:
 ORA-00911: 无效字符 SQL> Select to_date('20090210','yyyyMMdd'‟) from dual;
 Select to_date('20090210','yyyyMMdd'?) from dual
                                     *
 第 1 行出现错误:
 ORA-00911: 无效字符 SQL> Select to_date('20090210','yyyyMMdd') from dual;
TO_DATE('20090
 --------------
 10-2月 -09SQL> select empno, ename, sal,
   2  case deptno
   3  when 10 then '财务部'
   4  when 20 then '研发部'
   5  when 30 then '销售部'
   6  else '未知部门'
   7  end 部门
   8  from emp;
 from emp
        *
 第 8 行出现错误:
 ORA-00942: 表或视图不存在 SQL> select empno, lpad(initcap(trim(ename)),10,' ') name, job, sal from emp;
 select empno, lpad(initcap(trim(ename)),10,' ') name, job, sal from emp
                                                                     *
 第 1 行出现错误:
 ORA-00942: 表或视图不存在 SQL> 从 Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - 64bit Produc
 tion
 With the Partitioning, OLAP, Data Mining and Real Application Testing options 断
 开C:\Users\yuehui>
C:\Users\yuehui>
C:\Users\yuehui>