plsql常用方法在SQLPLUS下,实现中-英字符集转换alter session set nls_language='AMERICAN';alter session set nls_language='SIMPLIFIED CHINESE';主要知识点:一、有关表的操作1)建表create table test as select * from dept; --从已知表复制数据和结构create table test as select * from dept where 1=2; --从已知表复制结构但不包括数据2)插入数据:insert into test select * from dept;二、运算符算术运算符:+ - * / 可以在select 语句中使用连接运算符:|| select deptno|| dname from dept;比较运算符:> >= = != < <= like between is null in逻辑运算符:not and or集合运算符:intersect ,union,union all,minus要求:对应集合的列数和数据类型相同查询中不能包含long 列列的标签是第一个集合的标签使用order by时,必须使用位置序号,不能使用列名例:集合运算符的使用:intersect ,union,union all,minusselect * from emp intersect select * from emp where deptno=10 ;select * from emp minus select * from emp where deptno=10;select * from emp where deptno=10 union select * from emp where deptno in (10,20); --不包括重复行select * from emp where deptno=10 union all select * from emp where deptno in (10,20); --包括重复行三,常用ORACLE 函数sysdate为系统日期dual为虚表一)日期函数[重点掌握前四个日期函数]1,add_months[返回日期加(减)指定月份后(前)的日期]select sysdate S1,add_months(sysdate,10) S2,add_months(sysdate,5) S3 from dual;2,last_day [返回该月最后一天的日期]select last_day(sysdate) from dual;3,months_between[返回日期之间的月份数]select sysdate S1, months_between('1-4月-04',sysdate) S2,months_between('1-4月-04','1-2月-04') S3 from dual4,next_day(d,day): 返回下个星期的日期,day为1-7或星期日-星期六,1表示星期日select sysdate S1,next_day(sysdate,1) S2,next_day(sysdate,'星期日') S3 FROM DUAL5,round[舍入到最接近的日期](day:舍入到最接近的星期日)select sysdate S1,round(sysdate) S2 ,round(sysdate,'year') YEAR,round(sysdate,'month') MONTH ,round(sysdate,'day') DAY from dual6,trunc[截断到最接近的日期]select sysdate S1,trunc(sysdate) S2,trunc(sysdate,'year') YEAR,trunc(sysdate,'month') MONTH ,trunc(sysdate,'day') DAY from dual7,返回日期列表中最晚日期select greatest('01-1月-04','04-1月-04','10-2月-04') from dual二)字符函数(可用于字面字符或数据库列)1,字符串截取select substr('abcdef',1,3) from dual2,查找子串位置select instr('abcfdgfdhd','fd') from dual3,字符串连接select 'HELLO'||'hello world' from dual;4, 1)去掉字符串中的空格select ltrim(' abc') s1,rtrim('zhang ') s2,trim(' zhang ') s3 from dual2)去掉前导和后缀select trim(leading 9 from 9998767999) s1,trim(trailing 9 from 9998767999) s2,trim(9 from 9998767999) s3 from dual;5,返回字符串首字母的Ascii值select ascii('a') from dual6,返回ascii值对应的字母select chr(97) from dual7,计算字符串长度select length('abcdef') from dual8,initcap(首字母变大写),lower(变小写),upper(变大写)select lower('ABC') s1,upper('def') s2,initcap('efg') s3 from dual;9,Replaceselect replace('abc','b','xy') from dual;10,translateselect translate('abc','b','xx') from dual; -- x是1位11,lpad [左添充] rpad [右填充](用于控制输出格式)select lpad('func',15,'=') s1, rpad('func',15,'-') s2 from dual;select lpad(dname,14,'=') from dept;12, decode[实现if ..then 逻辑]select deptno,decode(deptno,10,'1',20,'2',30,'3','其他') from dept;三)数字函数1,取整函数(ceil 向上取整,floor 向下取整)select ceil(66.6) N1,floor(66.6) N2 from dual;2, 取幂(power) 和求平方根(sqrt)select power(3,2) N1,sqrt(9) N2 from dual;3,求余select mod(9,5) from dual;4,返回固定小数位数(round:四舍五入,trunc:直接截断)select round(66.667,2) N1,trunc(66.667,2) N2 from dual;5,返回值的符号(正数返回为1,负数为-1)select sign(-32),sign(293) from dual;四)转换函数1,to_char()[将日期和数字类型转换成字符类型]1) select to_char(sysdate) s1,to_char(sysdate,'yyyy-mm-dd') s2,to_char(sysdate,'yyyy') s3,to_char(sysdate,'yyyy-mm-dd hh12:mi:ss') s4,to_char(sysdate, 'hh24:mi:ss') s5,to_char(sysdate,'DAY') s6 from dual;2) select sal,to_char(sal,'$99999') n1,to_char(sal,'$99,999') n2 from emp2, to_date()[将字符类型转换为日期类型]insert into emp(empno,hiredate) values(8000,to_date('2004-10-10','yyyy-mm-dd')); 3, to_number() 转换为数字类型select to_number(to_char(sysdate,'hh12')) from dual; //以数字显示的小时数五)其他函数user:返回登录的用户名称select user from dual;vsize:返回表达式所需的字节数select vsize('HELLO') from dual;nvl(ex1,ex2):ex1值为空则返回ex2,否则返回该值本身ex1(常用)例:如果雇员没有佣金,将显示0,否则显示佣金select comm,nvl(comm,0) from emp;nullif(ex1,ex2):值相等返空,否则返回第一个值例:如果工资和佣金相等,则显示空,否则显示工资select nullif(sal,comm),sal,comm from emp;coalesce:返回列表中第一个非空表达式select comm,sal,coalesce(comm,sal,sal*10) from emp;nvl2(ex1,ex2,ex3) :如果ex1不为空,显示ex2,否则显示ex3如:查看有佣金的雇员姓名以及他们的佣金select nvl2(comm,ename,') as HaveCommName,comm from emp;六)分组函数max min avg count sum1,整个结果集是一个组1) 求部门30 的最高工资,最低工资,平均工资,总人数,有工作的人数,工种数量及工资总和select max(ename),max(sal),min(ename),min(sal),avg(sal),count(*) ,count(job),count(distinct(job)) ,sum(sal) from emp where deptno=30;2, 带group by 和having 的分组1)按部门分组求最高工资,最低工资,总人数,有工作的人数,工种数量及工资总和select deptno, max(ename),max(sal),min(ename),min(sal),avg(sal),count(*) ,count(job),count(distinct(job)) ,sum(sal) from emp group by deptno;2)部门30的最高工资,最低工资,总人数,有工作的人数,工种数量及工资总和select deptno, max(ename),max(sal),min(ename),min(sal),avg(sal),count(*) ,count(job),count(distinct(job)) ,sum(sal) from emp group by deptno having deptno=30;3, stddev 返回一组值的标准偏差select deptno,stddev(sal) from emp group by deptno;variance 返回一组值的方差差select deptno,variance(sal) from emp group by deptno;4, 带有rollup和cube操作符的Group Byrollup 按分组的第一个列进行统计和最后的小计cube 按分组的所有列的进行统计和最后的小计select deptno,job ,sum(sal) from emp group by deptno,job;select deptno,job ,sum(sal) from emp group by rollup(deptno,job);cube 产生组内所有列的统计和最后的小计select deptno,job ,sum(sal) from emp group by cube(deptno,job);七、临时表只在会话期间或在事务处理期间存在的表.临时表在插入数据时,动态分配空间create global temporary table temp_dept(dno number,dname varchar2(10))on commit delete rows;insert into temp_dept values(10,'ABC');commit;select * from temp_dept; --无数据显示,数据自动清除on commit preserve rows:在会话期间表一直可以存在(保留数据)on commit delete rows:事务结束清除数据(在事务结束时自动删除表的数据)1.0摘要//简要说明该文档内容SQL是用来访问关系型数据库一种通用语言,其执行特点是非过程化,即不用指明执行的具体方法和途径,而是简单的调用相应语句来直接取得结果即可。