oracle,简单来说就是数据库,数据库 ,顾名思义,就是存放数据的容器!!
不知道oracle的我先科普一下吧~~~科普,科学普及简称科普,又称大众科学或者普及科学,是指利用各种传媒以浅显的、让公众易于理解、接受和参与的方式向普通大众介绍自然科学和社会科学知识、推广科学技术的应用、倡导科学方法、传播科学思想、弘扬科学精神的活动。
nice,科普完毕,接下来废话不多说了,直接上代码案例,前人说:脑子是个好东西,得用起来!!!后人补充到:古人说的对!!!
select * from scott.emp; select eName from scott.emp; select rowid,ename from scott.emp where ename='SMITH'; select emp.*,rownum from scott.emp where rownum<11; --创建学员信息表 create table student ( stuNo char(6) not null, stuName varchar2(20) not null, stuAge number(3,0) not null, stuID number(18,0), stuSeat number(2,0) ); insert into stuinfo(stuNo,stuname,stuAge,stuSeat)values('2','活动',25,3) select * from stuinfo --查询表的位置 select tablespace_name,table_name from user_tables where table_name=upper('stuinfo'); --创建表空间 create tablespace test datafile 'D:\oracle\shujuku\test.ora' size 1000M; create user test identified by test default tablespace test quota 500M on users; grant all privileges to test; --查看表空间 select file_name,tablespace_name,bytes,autoextensible from dba_data_files where tablespace_name='test'; select * from test.stuinfo; --提交事务 commit; select * from scott.emp; --修改密码 alter user system identified by 123; select * from scott.emp; --rowid伪列数据对象编号 文件编号 块编号 行编号 select e.*,rowid from scott.emp e; --rownum,从1开始,大于1的东西查不出来,小于等于某个值可以查询 select e.*,rownum from scott.emp e where rownum<=10; select * from scott.dept; insert into scott.dept(deptno,dname,loc)values('5','1111','dsds'); commit; delete from scott.dept where deptno='5' ;commit; -- --创建学员信息表 create table student ( stuNo number not null, stuName varchar2(20) not null, stuAge number(3,0) not null, stuSeat number(2,0) ); select * from student insert into student(stuNo,stuname,stuAge,stuSeat)values('1','张三',18,1); insert into student(stuNo,stuname,stuAge,stuSeat)values('2','李四',20,2); insert into student(stuNo,stuname,stuAge,stuSeat)values('3','王五',15,3); insert into student(stuNo,stuname,stuAge,stuSeat)values('4','张三',18,4); insert into student(stuNo,stuname,stuAge,stuSeat)values('5','张三',20,5); --事务的处理 --没有添加进去编号8 insert into student(stuNo,stuname,stuAge,stuSeat)values('6','王五1',12,6); insert into student(stuNo,stuname,stuAge,stuSeat)values('7','张三1',14,7); savepoint a; insert into student(stuNo,stuname,stuAge,stuSeat)values('8','张三',20,5); rollback to savepoint a; commit; select * from test.student; --选择无重复的行distinct select distinct stuname from student; --选择重复的行distinct(姓名和年龄) select distinct stuname ||stuage from student; /* 注释的重要性 */ --别名 select distinct stuname "姓名" from student; --复制一个表 as后边加一个select create table newstudent1 as select * from student; select * from newstudent1 ; --复制表的结构(不包括数据) create table newstudent as select * from student where 1=2; select * from newstudent; --查询表中的记录数 select count(1) from student; --查询姓名和年龄中不存在重复的记录 --大于等于是查询重复的,小于是查询不重复的 select stuname,stuage from student group by stuname,stuage having(count(stuname||stuage)<2); select stuname,stuage from student group by stuname,stuage having(count(stuname||stuage)>1); select stuname from student group by stuname having(count(stuname)<5); --查询用户数量大于10的 select * from user_all_tables a where a.num_rows>1; --添加列,删除列 alter table student add(phone varchar2(20), emil varchar2(20)); alter table student drop(phone); select * from student; select * from stuinfo; select stuname from student group by stuname having(count(stuname)>1); /* oracle的日期函数last_day 意思是得到每月的最后一天,用这个函数,我们可以得到各种不同的日期. 1:得到当前月第一天与最后一天 */ select to_char(trunc(sysdate,'MONTH'),'yyyymmdd') firstday , to_char(last_day(trunc(sysdate,'MONTH')),'yyyymmdd') lastday from dual; --2:得到上月第一天与上月最后一天 SELECT to_char( last_day(add_months(SYSDATE, -2)) + 1 ,'yyyymmdd') firstday ,to_char(last_day(add_months(SYSDATE, -1)),'yyyymmdd') lastday FROM dual; --3:得到上上个月第一天与上上个月最后一天 SELECT to_char( last_day(add_months(SYSDATE, -3)) + 1 ,'yyyymmdd') firstday ,to_char(last_day(add_months(SYSDATE, -2)),'yyyymmdd') lastday FROM dual; --4:得到下个月第一天与下个月最后一天 SELECT to_char( last_day(add_months(SYSDATE, 0)) + 1 ,'yyyymmdd') firstday ,to_char(last_day(add_months(SYSDATE, 1)),'yyyymmdd') lastday FROM dual;
nice,有的人可能之前没学过数据库,比如说my sql ,sql server 等等,直接上来就是oracle,所以,推荐一部视频,即使你没有学过sql server什么的,或者学过没深入理解的,那么,请点击 这里, 密码: 3ydr,一共46节课,足足够你学会oracle了,拿走不谢!!!