16.L:代表本地货币符，这个和区域有关。这个时候我们想来显示一下人民币的符号：￥
$ vi .bash_profile ---写入如下内容： export NLS_LANG='SIMPLIFIED CHINESE'_CHINA.AL32UTF8 ---修改成简体中文+地区+字符集 source .bash_profile ---让环境变量生效 [oracle@oracle ~]$ sqlplus scott/tiger SQL*Plus: Release 10.2.0.5.0 - Production on 星期五 8月 15 18:38:22 2014 Copyright (c) 1982, 2010, Oracle. All Rights Reserved. Connected to: Oracle Database 10g Enterprise Edition Release 10.2.0.5.0 - Production With the Partitioning, OLAP, Data Mining and Real Application Testing options SQL>---如果你是用x-shell或者putty远程连接linux的话，需要将你的客户端的字符集也改回来
17.TO_NUMBER:将一个字符串转化为数字
把十进制转换为十六进制：（to_char）
SQL> select to_char(10,'xxx') from dual; TO_CHAR(10,' ------------ a
把十六进制转换为十进制：（to_number）
SQL> select to_number('a','xxx') from dual; TO_NUMBER('A','XXX') -------------------- 10
18.日期的两位表示方式：RR和YY
SQL> select * from emp where hiredate=to_date('17-12-80','dd-mm-rr'); EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO ----- ------ --------- ----- ------------------- ----- ---------- ------ 7369 SMITH CLERK 7902 1980-12-17 00:00:00 800 20 日期的两位表示方式：RR和YY YY:始终与当前世纪一致 RR：得到的是与当前年最近的年份
19.操作NULL值的函数
NVL(expr1, expr2)
如果expr1为null,则返回expr2,否则返回expr1
可以使用的数据类型是数字、日期、字符型.
数据类型必须能够匹配（expr1和expr2的类型必须要一致）
SQL> select ename ,comm,nvl(comm,0) nvl from emp; ENAME COMM NVL ------------------------------ ---------- ---------- SMITH 0 ALLEN 300 300 WARD 500 500 JONES 0 MARTIN 1400 1400
20.NVL(expr1, expr2，expr2)
如果expr1非空，就返回expr2
如果expr1为空，就返回expr3
SQL> select ename,sal,comm,sal+comm,sal+nvl(comm,0),nvl2(comm,'工资加奖金','纯工资') "收入类别" from emp; ENAME SAL COMM SAL+COMM SAL+NVL(COMM,0) 收入类别 ------ ----- ---------- ---------- --------------- --------------- SMITH 800 800 纯工资 ALLEN 1600 300 1900 1900 工资加奖金 WARD 1250 500 1750 1750 工资加奖金 JONES 2975 2975 纯工资 MARTIN 1250 1400 2650 2650 工资加奖金 BLAKE 2850 2850 纯工资 CLARK 2450 2450 纯工资 SCOTT 4000 4000 纯工资 KING 5000 5000 纯工资 TURNER 1500 0 1500 1500 工资加奖金 ADAMS 1100 1100 纯工资 JAMES 950 950 纯工资 FORD 3000 3000 纯工资 MILLER 1300 1300 纯工资
21.NULLIF(expr1,expr2)
如果expr1和expr2相同就返回空，否则返回expr1
SQL> select ename,nullif(ename,'KING') from emp; ENAME NULLIF(ENAME,'KING') ------ ------------------------------ SMITH SMITH ALLEN ALLEN WARD WARD JONES JONES MARTIN MARTIN BLAKE BLAKE CLARK CLARK SCOTT SCOTT KING TURNER TURNER ADAMS ADAMS JAMES JAMES FORD FORD MILLER MILLER
22. COALESCE(expr1,expr2,expr3,…exprn)：返回括号内第一个非空的值
23.条件表达式函数
decode与case when
区别：
1. decode是oracle自己的函数，case when是SQL99标准函数
2. decode只能进行等值判断，case when可以进行非等值判断
SQL> select ename,job,case job when 'CLERK' then '1.clerk' when 'SALESMAN' then '2.saleman' else 'other' end from emp ENAME JOB CASEJOBWHEN'CLERK'THEN'1.CL ------ --------- --------------------------- SMITH CLERK 1.clerk ALLEN SALESMAN 2.saleman WARD SALESMAN 2.saleman JONES MANAGER other MARTIN SALESMAN 2.saleman BLAKE MANAGER other CLARK MANAGER other SCOTT ANALYST other KING PRESIDENT other TURNER SALESMAN 2.saleman ADAMS CLERK 1.clerk JAMES CLERK 1.clerk FORD ANALYST other MILLER CLERK 1.clerk
decode用法实例
SQL> select ename,decode(job,'SALESMAN','CLERK','UNKNOWN') from emp; ENAME DECODE(JOB,'SALESMAN' ------ --------------------- SMITH UNKNOWN ALLEN CLERK WARD CLERK JONES UNKNOWN MARTIN CLERK BLAKE UNKNOWN CLARK UNKNOWN SCOTT UNKNOWN KING UNKNOWN TURNER CLERK ADAMS UNKNOWN JAMES UNKNOWN FORD UNKNOWN MILLER UNKNOWN
使用case when进行非等值判断：
SQL> select ename,sal,case when sal between 700 and 1200 then 1 when sal between 1201 and 1400 then 2 when sal between 1401 and 2000 then 3 when sal between 2001 and 5000 then 4 else 5 end grade from emp ENAME SAL GRADE ------ ---------- ---------- SMITH 800 1 ALLEN 1600 3 WARD 1250 2 JONES 2975 4 MARTIN 1250 2 BLAKE 2850 4 CLARK 2450 4 SCOTT 3000 4 KING 5000 4 TURNER 1500 3 ADAMS 1100 1 JAMES 950 1 FORD 3000 4 MILLER 1300 2
24.函数的嵌套
单行的函数可以嵌套到任何一个层次
嵌套函数的计算顺序——先计算深层嵌套，再计算浅层嵌套.
SQL> select ename,mgr,nvl(to_char(mgr),'no manager') from emp; ENAME MGR NVL(TO_CHAR(MGR),'NOMANAGER') ------ ----- ---------------------------------------- SMITH 7902 7902 ALLEN 7698 7698 WARD 7698 7698 JONES 7839 7839 MARTIN 7698 7698 BLAKE 7839 7839 CLARK 7839 7839 SCOTT 7566 7566 KING no manager TURNER 7698 7698 ADAMS 7788 7788 JAMES 7698 7698 FORD 7566 7566 MILLER 7782 7782