0.常用命令
tnsping orcl（Transparent Network Substrate透明網絡底層）
查看監聽狀態lsnrctl status
監聽停止 lsnrctl stop
監聽啓動 lsnrctl start
sqlplus /nolog
conn /as sysdba
數據庫關閉 shutdown immediate,shutdown abort
數據庫啓動 startup
upgrade
select status from v$instance;
alter user scott account unlock;
alter user scott identified by bsoft;
1. oracle命令類別
數據庫操縱語言 DML：select,insert,delete,update,merge
merge into products p using newproducts np on (p.product_id = np.product_id)
when matched then
update set p.product_name = np.product_name
when not matched then
insert values(np.product_id, np.product_name, np.category)
數據定義語言 DDL：create ,alter,drop,truncate,rename,comment
create table TEST
（
ID VARCHAR2(10),
NAME VARCHAR2(30)
）;
ALTER TABLE test ADD address varchar2(20);
ALTER TABLE test MODIFY address varchar2(30);
ALTER TABLE test RENAME column address TO newaddress;
ALTER TABLE test DROP COLUMN newaddress;
ALTER TABLE test RENAME TO test1;
rename test1 to test;
comment on table test is '測試表';
select * from user_tab_comments where TABLE_NAME='TEST';
comment on column TEST.NAME is '名稱' ;
select * from user_col_comments where TABLE_NAME='TEST' and column_name='NAME';
事務控制語言 TCL: commit,rollback,savepoint
insert into test values(1,'a');
savepoint A;
insert into test values(2,'b');
savepoint B;
insert into test values(3,'c');
savepoint C;
rollback to A;
commit;
數據控制語言 DCL: grant,revoke
grant dba to scott;
revoke dba from scott;
2.常用函數
字符函數
select upper('bsoft') from dual;
select initcap('bsoft') from dual;
select initcap('bSOFT') from dual;
select concat('welcome ',concat('to ','bsoft')) from dual;
select substr('welcome to bsoft',12,7) from dual;
select instr('welcome to bsoft','bsoft',11) from dual;
select length('bsoft張振磊') from dual;
select lengthb('bsoft張振磊') from dual;
select lpad('張振磊',10,'1') from dual;
select rpad('bsoft',11,'bsoft') from dual;
select replace('bsoft張振磊','張','zhang') from dual;
select trim('b' from 'bbbbsoftbzzlbb') from dual;
數值函數
select round(45.5,0) from dual;
select round(155.1,-1) from dual;
select round(155.1,-2) from dual;
select trunc(155.1) from dual;
select trunc(155.23,-1) from dual;
select mod(11,3) from dual;
日期函數
select to_date('2016.08.11 10:10:10','yyyy-mm-dd hh24:mi:ss') from dual;
select sysdate + 10 from dual;
select sysdate,sysdate + 10/24 from dual;
select ename,hiredate,sysdate,(sysdate - hiredate)/365 from scott.emp;
select ename,hiredate,sysdate,months_between(sysdate,hiredate)/12 from emp;
select add_months(sysdate,1) from dual;
select last_day(sysdate) from dual;
select next_day(sysdate,7) from dual;
select round(sysdate,'month') from dual;
select trunc(sysdate+10,'month') from dual;
select round(sysdate,'year') from dual;
select trunc(sysdate,'year') from dual;
幾個有用的函數
select job,sal,decode(job,'CLERK',sal*1.1,'SALESMAN',sal*1.2,sal) from emp；
select job,sal,case job when 'CLERK' then sal*1.1 when 'SALESMAN' then sal*1.2 else sal end from emp；
select job,sal,case when job='CLERK' then sal*1.1 when job='SALESMAN' then sal*1.2 else sal end from emp；
select case when 1=1 then 2 when 2=2 then 3 end from dual；
select ename,job,sal,case when sal>=5000 then '高級' when sal >=3000 then '中級' else '低級' end from emp；
select distinct job from emp；
select sys_context('userenv','ip_address') from dual;
select sys_context('userenv','sid') from dual；
select sys_context('userenv','terminal') from dual
select ascii('d') from dual;
select chr(100) from dual;
3.sql數據類型
字符型
char()固定字長 最大2000
varchar2()可變字長 最大4000
create table test(a char(3));
insert into test
select 1 from dual;
select length(a) from test;
create table test2(a varchar(3))
insert into test2
select 1 from dual;
select length(a) from test2;
alter user scott quota unlimited on users;
數值型
number(p,s)
int
create table test3(a number(4,2));
insert into test3
values(111.11);
create table test4(a int);
insert into test4
values(111.11);
commit;
select * from test4;
日期型
date
timestamp
timestamp with time zone
timestamp with local time zone
create table test5(a date,b timestamp,c timestamp with time zone,d timestamp with local time zone);
insert into test5
values(sysdate,sysdate,sysdate,sysdate);
select * from test5
數據類型的轉換
隱性類型轉換，顯性類型轉換
隱性類型轉換
select * from emp where empno ='7788';
select length(sysdate) from dual;
length(sysdate) =9？
select * from nls_session_parameters where parameter='NLS_DATE_FORMAT';
select * from nls_instance_parameters where parameter='NLS_DATE_FORMAT';
select * from nls_database_parameters where parameter='NLS_DATE_FORMAT';
千年蟲
select '12.5' + 11 from dual;
select 10 + '12.5' ||11 from dual;
select 10 + ('12.5' ||11) from dual
顯性類型轉換
to_char
to_date
to_number
select ename,to_char(hiredate,'DD-MON-YY') from emp;
select ename,to_char(hiredate,'yyyy-mm-dd'),to_char(hiredate,'fmyyyy-mm-dd') from emp;
select ename,sal,to_char(sal,'L999.99') from emp;
select to_date('2016.08.31','yyyy.mm.dd') from dual;
select to_number('$2016','$9999.99') from dual;
4.where 子句中常用的運算符
算數運算符
+-*/
邏輯運算符
not ,and ,or
比較運算符
單行比較=,>,>=,<=,<
多行比較符>any,>all,<any,<all,in,not in
模糊比較like(%,_)
特殊比較is null
()優先級最高
between and
select ename,sal from emp where sal between 3000 and 5000;
轉義
create table test6(a varchar(20));
insert into test6
values('AZZL');
insert into test6
values('A%ZZL');
select * from test6 where a like 'A%%'
select * from test6 where a like 'A\%%' escape '\'
'' 和 ""
''內表示字符
"" 別名 ，保持原樣
select a from test6
select "a" from test6
select "A" from test6
連續兩個'表示轉義
select empno||'''s name is ' ||ename from emp
in 檢驗一個值是否在一個列表中
select * from emp where empno in(7788,7900)
交互輸入變量符&
select * from emp where empno=&emp_no
使用邏輯操作符
select * from emp where sal >1000 and job ='CLERK';
select * from emp where sal >1000 or job ='CLERK';
select * from emp where job not in('CLERK');
5.分組函數
最重要的5個分組函數
sum(),avg(),count(),max(),min()
select sum(sal) sum,avg(sal) avg,max(sal) max,min(sal) min ,count(*) count from emp;
select job, sum(sal) sum,avg(sal) avg,max(sal) max,min(sal) min ,count(*) count from emp group by job;
select min(hiredate),max(hiredate) ,min(ename),max(ename) from emp ;
select count(*),count(comm) from emp ;
select deptno,avg(comm) from emp group by deptno;
select deptno,avg(nvl(comm,0)) from emp group by deptno;
group by 創建組
一旦使用了group by ，select後面只能有兩種列：組函數和分組特性列
select deptno,avg(sal) from emp group by deptno having avg(sal)>2000；
select deptno,avg(sal) from emp where avg(sal)>2000 group by deptno；
select deptno,avg(sal) from emp where sal>2000 group by deptno；
select deptno,avg(sal) from emp group by deptno having avg(sal)>2000 order by avg(sal);
select deptno,avg(sal) from emp group by deptno having avg(sal)>2000 order by job;
select from where group by having order by
分組函數的嵌套
單行函數可以嵌套任意層，分組函數最多可以嵌套兩層
select sum(sal) from emp group by deptno;
select avg(sum(sal)) from emp group by deptno;
select count(avg(sum(sal))) from emp group by deptno;
6.數據限定與排序
where限定 from後面的表或視圖，限定的選項只能是表的列或列單行函數或列表達式，where後不可以直接使用分組函數
select job,ename,sal from emp where sal >2000;
select job,ename,sal from emp where length(sal)>3;
select job,ename,sal from emp where sal +comm >2000;
having 限定group by的結果，限定的選項必須是group by 後的聚合函數或分組列，不可以直接使用where後的限定選項
select deptno,sum(sal) from emp group by deptno having deptno=10;
select deptno,sum(sal) from emp group by deptno having sum(sal)>8000;
排序
order by 總是在一個select語句的最後邊
排序可以使用列名，列表達式，列函數，列別名，列位置編號，select的投影列可不包含排序列，除指定的列位置編號外
升序asc 降序 desc，有空值的列的排序，缺省（升序）時，null排在最後面
使用多個列排序，多列用逗號隔開，每列後面可以指定升降序
select ename,sal from emp order by sal；
select ename,sal salary from emp order by salary；
select ename,sal salary from emp order by 2；
select ename,sal,comm ,sal+comm from emp order by sal +comm；
select deptno,avg(sal) from emp group by deptno order by avg(sal) desc；
select ename,job,sal+comm from emp order by 3 desc；
select ename,job,sal+comm from emp order by 3 desc nulls last；
select ename,job,deptno from emp order by deptno asc,job desc；