select 2*3 from dual; --求年薪
select ename,sal, sal*12 from emp;
--别名
select ename,sal, sal*12 as "年薪" from emp;
select ename,sal, sal*12  "年薪" from emp; --员工一年总收入
select * from emp;select ename,sal, sal*12+comm as "年总收入" from emp;
--注意：含有任何null值的数学表达式最后的结果都为null --字符串连接符 ||
select ename||'员工姓名' from emp;--处理一个字符串中含有单引号的情况 :使用2个单引号表示一个单引号
select ename||'员工''姓名' from emp;--含有任何null值的字符串表达式中，null被当作空字符串处理
select empno, ename||mgr from emp;--求员工每个级别顶薪select hisal*12 as "员工年顶薪" from salgrade;/*  distinct  消除重复值   */
--求emp表中的部门列表
select distinct deptno  from emp;select  deptno, job  from emp;
select distinct deptno, job  from emp;--去除deptno, job 组合起来的重复值--null值
--求奖金为null的员工信息
select * from emp where comm is null;--求奖金不为null的员工信息
select * from emp where comm is not null;/*    in    */
--求员工编号在某一个集合内的值
select * from emp where empno in (7369,7499,7521)select * from emp where empno  not in (7369,7499,7521)/*  oracle 日期 */select * from emp;  --求入职日期在1982-1-23后入职的人select * from emp where hiredate > '23-1月-82';/*  like   */--查询员工 名字第二个字面为A的人select * from emp where ename like '_A%';--查询名字中含有 % 等通配符的数据时，使用转义字符 \   (\%)
select * from emp where ename like '%\%%';--查询1987年入职的人
select * from emp where hiredate>='1-1月-87' and hiredate<='31-12月-87';select * from emp where hiredate like '%87%' /* order by*/select * from emp order by deptno asc,sal desc;/*常用函数*/
--lower()select empno,  Lower(ename)  from emp;--查询名字带有 “A“ 或 "a"的员工
select *  from emp where ename like '%A%' or ename like '%a%';select *  from emp where Lower(ename) like '%a%';--Upper();  小写转大写select Upper('wepull') from dual;--Substr
select Substr('wepull',2,3) from dual; --epu
select Substr('wepull',2) from dual; --epullselect Substr(ename,2) from emp;--Chr()  某个ASCII码值对应的字符
select Chr(97) from dual; -- a-- Ascii()函数
--例子：求一个字符的ASCII码值
select Ascii('a') from dual;  --97--常用数值函数select round(23.652) from dual --24select round(23.652,2) from dual  --23.65select round(23.652,-1) from dual  --20
select round(493.652,-2) from dual  --500--to_char()select to_char(456123.45,'L999,999.99') from dual--  ￥456,123.00--to_char()对日期的转换select sysdate from dual;select to_char(sysdate,'YYYY/MM/DD') from dual;--to_date()函数--例子:将1985年2月14日8:00以后入职的雇员信息取出select * from emp where hiredate > to_date('1985-02-14 8:00','YYYY-MM-DD HH:MI')--to_number()函数--求薪水<于1200的人
select * from emp where sal<to_number('$1,200','$9,999')--nvl 处理空值select ename, sal*12+comm  as "一年总收入" from emp select ename, sal*12+nvl(comm,0)  as "一年总收入"  from emp ---聚合函数/组函数
select * from emp;--emp表中deptno数量
select count(deptno) from emp;select count(distinct deptno) as "部门总数" from emp;--group by--求每个部门的最大工资
select  deptno ,max(sal) from emp group by deptno;--求每个部门中职位的最大工资
select  deptno ,job,max(sal) from emp group by deptno , job;---求每个部门工资最高人信息select ename,deptno,sal from emp where (deptno,sal)in
(select  deptno ,max(sal) from emp group by deptno);--方法二
select * from emp join(select  deptno ,max(sal) max_sal from emp group by deptno  ) t on (emp.deptno=t.deptno and emp.sal=t.max_sal)--having
select deptno, avg(sal)  from emp group by deptno having avg(sal)>2500---子查询
--求工资最高的人的信息
select * from emp where sal=(select max(sal) from emp
);--rownum（分页）--查询emp表前5条记录select ename,rownum from emp where rownum<=5;--查询emp表第5条以后记录select * from (select empno, ename,rownum as r from emp)where r>5;--rownum 与排序select empno,ename,sal ,rownum from emp order by sal;select empno,ename,sal ,rownum from(select empno,ename,sal  from emp order by sal)上司
--自连接
--求emp表中员工的姓名和对应的上司（mgr）
select * from emp;select e1.ename, e2.ename
from emp e1,emp e2
where e1.mgr=e2.empno;--交叉连接
select ename from emp;
select dname from dept;select ename,dname  from emp ,dept; --结果为笛卡尔乘积--SQL1999 语法
select ename,dname  from emp cross join dept; --连接查询
create table a(id int primary key,name nvarchar2(20)
);
select  * from a;
insert into a values (1,'凤姐');
insert into a values (3,'犀利哥');
insert into a values (5,'春哥');
insert into a values (6,'曾哥');
insert into a values (7,'平平');create table b(id int primary key,info nvarchar2(20)
)insert into b values (1,'深圳');
insert into b values (2,'武汉');
insert into b values (6,'成都');select  * from a;
select  * from b;select  * from a  left outer join b on a.id=b.id;--左外连接
select * from a right outer join b on  (a.id=b.id);--右外连接
select * from a full  join b on  (a.id=b.id);--全连接 （左外连接+右外连接）
select * from a inner join b on  (a.id=b.id) --内连接--非等值连接
--查询出雇员名字和薪水等级（2个表连接查询）
select * from emp;
select * from salgrade;select e.ename ,e.sal ,s.grade from emp e
join salgrade s
on (e.sal between s.losal  and s.hisal)--查询出雇员名字，及对应的部门名称，薪水等级（3个表连接查询）
select e.ename, d.dname, s.grade from emp ejoin dept d on(e.deptno=d.deptno)join salgrade s on (e.sal between s.losal  and s.hisal)--练习
--求部门中薪水最高的人名。select * from emp e;
select e.deptno, max(e.sal) from emp e group by deptno ;select e.ename ,t.deptno,e.sal from emp e
join (select e.deptno, max(e.sal) max_sal from emp e group by deptno) t
on (e.deptno=t.deptno and e.sal =max_sal)--求部门平均薪水等级？select deptno, avg(sal) from emp e group by deptno;
select * from salgrade;select t.deptno, t.avg_sal, s.grade from salgrade s
join (select deptno, avg(sal) avg_sal from emp e group by deptno) t
on(t.avg_sal between s.losal and s.hisal );     --求哪些人是经理
select * from emp;select * from emp where mgr in (select mgr from emp);select * from emp where mgr in (select distinct mgr from emp);      --平均薪水最高的部门编号与薪水  --第一步：先求出部门平均薪水select e.deptno ,avg(sal) from emp e group by e.deptno;--第二步：求出平均薪水最高值select max(t.avg_sal) from (select e.deptno ,avg(sal) avg_sal from emp e group by e.deptno) t      --综合     select deptno ,avg_sal from(select e.deptno ,avg(sal) avg_sal from emp e group by e.deptno) twhere  t.avg_sal =( select max(t.avg_sal) from (select e.deptno ,avg(sal) avg_sal from emp e group by e.deptno) t      )
--方法二：       select deptno ,avg_sal from(select e.deptno ,avg(sal) avg_sal from emp e group by e.deptno) t where  avg_sal =(select max(avg(sal)) from emp group by deptno )   --注意 :组函数嵌套只能嵌套2层 select * from emp;
--比普通员工的最高薪水还要高的经理人名称
-- 1.先求普通员工的最高薪水？  select max(sal) from emp e where e.empno  not in (select mgr from emp where mgr is not null )
--2.求比上面的值要大，并且还是经理人select e.ename,e.sal from emp e where e.empno  in (select distinct mgr from emp where mgr is not null )and e.sal>( select max(sal) from emp e where e.empno  not in (select distinct mgr from emp where mgr is not null ));--复制表create table emp as select * from scott.emp where 1<>1;--只复制结构
create table emp as select * from scott.emp ;--复制数据
create table dept as select * from scott.dept ;
create table salgrade as select * from scott.salgrade ;
create table bonus as select * from scott.bonus ;select * from emp---Orcle 高级部分--视图select * from scott.emp;create view  emp_view
as
select empno, ename,sal from scott.emp;select * from emp_view;drop view emp_view;--查询每个部门的名称、总人数、平均工资、最低工资的员工名字。
select dept.dname from demp;select deptno, count(empno) ,avg(sal),min(sal) from emp group by deptno ;  --综合： 3张表连接查询
select d.dname, t.deptno, t.c, t.avg_sal,t.min_sal ,e.ename
from dept djoin (select deptno, count(empno) c ,avg(sal) avg_sal,min(sal) min_sal from emp group by deptno ) ton (d.deptno=t.deptno)join emp eon (e.sal=t.min_sal and e.deptno=t.deptno)--把上面结果封装成视图
create or replace view deptInfo_view
as
select d.dname, t.deptno, t.c, t.avg_sal,t.min_sal ,e.ename
from dept djoin  (select deptno, count(empno) c ,avg(sal) avg_sal,min(sal) min_sal from emp group by deptno ) ton (d.deptno=t.deptno)join emp eon (e.sal=t.min_sal and e.deptno=t.deptno)--
select * from deptinfo_view;-----------外键约束
drop table t_type;
create table t_type(id int primary key,typeName varchar2(20))
drop table t_book;
create table t_book(id int primary key,name varchar2(20) ,tid int ,constraint FK_tid  foreign key (tid) references t_type(id)--字段级的外键约束，不用加foreign key)--
select * from user_tables;
select table_name from user_tables;insert into t_type values (1,'言情类');
insert into t_type values (2,'计算机类');
insert into t_type values (3,'言武侠类');select * from t_book t
insert into t_book values (1,'小磊子的情书',1);
insert into t_book values (2,'凤姐的韵事',1);
insert into t_book values (3,'干露露的视频',2);
insert into t_book values (4,'java自学成才',2);
insert into t_book values (5,'刘德华的情歌',3);
----------视图中使用DML的规定（不重要）create or replace view book_view
as
select id,name from t_book;--
select * from t_book
select * from book_view;delete from book_view where id=4;--只读视图create or replace view book_view
as
select id,name from t_book
with read only;--序列
create or replace sequence my_sec;select  my_sec.nextval  from dual;
select  my_sec.currval  from dual;create  sequence book_sec;create table book(id number,name varchar2(50)
)
alter table book add constraint PK_id primary key (id)select * from book;insert into book values (book_sec.nextval,'111');
insert into book values (book_sec.nextval,'222');
insert into book values (book_sec.nextval,'333');
insert into book values (book_sec.nextval,'444');create sequence se_1
increment by 50 --次增长的幅度 50
start with 100  --从100开始
maxvalue 400  --最大400
minvalue 50
cycle  --到最大值后循环
cache 2;select se_1.nextval from dual--索引
create index idx_book on book(name);
drop index idx_book;--同义词
t_bookcreate synonym t for t_book
select * from t;drop synonym t;--- PL/SQL
begindbms_output.put_line('hello word');
end;--变量赋值
declarev_name varchar2(20):='wepull';
begindbms_output.put_line(v_name);
end;     --复合类型变量--记录类型
declare--定义一个记录类型type book_rec is record(id int,name varchar2(20));b_rec book_rec;       --声明一个变量是记录类型
beginselect id ,name into b_rec from wepull.t_book where id=1;dbms_output.put_line(b_rec.id||b_rec.name);
end;--%typedeclare v_id wepull.t_book.id%type ;--定义的变量v_id类型与t_book中的id列的类型一致v_name wepull.t_book.name%type;
begin/*v_id:=1;v_name:='wepull';*/select id ,name into v_id,v_name from wepull.t_book where id=1;dbms_output.put_line(v_id);dbms_output.put_line(v_name);
end;--rowtypedeclare v_book wepull.t_book%rowtype ;--定义的变量v_book类型与t_book中列的类型一致
beginselect * into v_book from wepull.t_book where id=1;dbms_output.put_line('id: '||v_book.id);dbms_output.put_line('name: '||v_book.name);dbms_output.put_line('tid: '||v_book.tid);
end;--嵌套表
select * from t_book;select * from wepull.t_book;declaretype book_table_type is table of wepull.t_book%rowtype;--定义类型v_book book_table_type:=book_table_type();
beginv_book.extend(5);select * into v_book(1)  from wepull.t_book where id=1;dbms_output.put_line(v_book(1).id||' '||v_book(1).name);select * into v_book(2)  from wepull.t_book where id=2;dbms_output.put_line(v_book(2).id||' '||v_book(2).name);
end;
/
--流程控制语句--if --单个if
--1.查询用户输入的id的图书，如果图书的tid=1 则输出图书类型为言情类
declarev_id wepull.t_book.id%type:=&v_id;v_tid wepull.t_book.tid%type;
beginselect id,tid into v_id, v_tid from wepull.t_book where id=v_id;if (v_tid=1) thendbms_output.put_line('此id的图书为言情类');end if;
end;
/--if else
--1.查询用户输入的id的图书，如果图书的tid=1 则输出图书类型为言情类，否则输出不是言情类
declarev_id wepull.t_book.id%type:=&v_id;v_tid wepull.t_book.tid%type;
beginselect id,tid into v_id, v_tid from wepull.t_book where id=v_id;if (v_tid=1) thendbms_output.put_line(v_id|| ' :此id的图书为言情类');elsedbms_output.put_line(v_id|| ' :此id的图书不是言情类');  end if;
end;
/--
--if elsif--1.查询用户输入的id的图书，
--如果图书的tid=1 则输出图书类型为言情类，
--如果图书的tid=2 则输出图书类型为计算机类
--如果图书的tid=3 则输出图书类型为言武侠类select * from wepull.t_type;declarev_id wepull.t_book.id%type:=&v_id;v_tid wepull.t_book.tid%type;
beginselect id,tid into v_id, v_tid from wepull.t_book where id=v_id;if (v_tid=1) thendbms_output.put_line(v_id|| ' :此id的图书为言情类');elsif(v_tid=2)thendbms_output.put_line(v_id|| ' :此id的图书为计算机类');  elsif(v_tid=3)thendbms_output.put_line(v_id|| ' :此id的图书为武侠类');  end if;
end;
/--case
declarev_id wepull.t_book.id%type:=&v_id;v_tid wepull.t_book.tid%type;v_typeName wepull.t_type.typeName%type;
beginselect tid into v_tid from wepull.t_book where id = v_id;v_typeName :=case v_tidwhen 1 then '言情类'when 2 then '计算机类'when 3 then '武侠类'else '其他类'end;dbms_output.put_line('id: '||v_id);dbms_output.put_line('tid: '||v_tid);dbms_output.put_line('typeName: '||v_typeName);
end;
/--
--case 搜索方式
declarev_id wepull.t_book.id%type:=&v_id;v_tid wepull.t_book.tid%type;v_typeName wepull.t_type.typeName%type;
beginselect tid into v_tid from wepull.t_book where id = v_id;v_typeName :=case when v_tid=1 then '言情类'when v_tid=2 then '计算机类'when v_tid=3 then '武侠类'else '其他类'end;dbms_output.put_line('id: '||v_id);dbms_output.put_line('tid: '||v_tid);dbms_output.put_line('typeName: '||v_typeName);
end;
/--循环
--循环1---Loop
--求 1+2+....+100=？declarev_i number:=0;v_sum number:=0;
beginloopv_i:=v_i+1;v_sum:=v_sum+v_i;exit when(v_i=100);end loop;   dbms_output.put_line('1+2+....+100='||v_sum);
end;
/--循环1---while
--求 1+2+....+100=？declarev_i number:=0;v_sum number:=0;
beginwhile(v_i<100) loopv_i:=v_i+1;v_sum:=v_sum+v_i;end loop;   dbms_output.put_line('1+2+....+100='||v_sum);
end;
/--循环1---for
--求 1+2+....+100=？declarev_i number:=0;v_sum number:=0;
beginfor v_i in 1..100 loopv_sum:=v_sum+v_i;end loop;dbms_output.put_line('1+2+....+100='||v_sum);
end;
/
--
declarev_i number:=0;v_sum number:=0;
beginfor int in 1..100 loopv_i:=v_i+1;v_sum:=v_sum+v_i;end loop;dbms_output.put_line('1+2+....+100='||v_sum);
end;
/--gotodeclarev_i number:=0;v_sum number:=0;
beginfor v_i in 1..10 loopdbms_output.put_line('当前i为： '||v_i);  if(v_i=5) thengoto endloop;end if;         end loop;<<endloop>>dbms_output.put_line('此时v_i=5,退出了循环体');
end;--null语句
--gotodeclarev_i number:=0;v_sum number:=0;
beginfor v_i in 1..10 loopdbms_output.put_line('当前i为： '||v_i);  if(v_i=5) thengoto endloop;end if;         end loop;<<endloop>>null;
end;--游标
--使用游标取出emp表总前10人的信息。
select * from scott.emp;declare--第一步：声明游标cursor emp_cursor is select * from scott.emp where rownum<=10; emp_record scott.emp%rowtype;
begin--第二步：打开游标open emp_cursor;--第三步：从游标中取数据loopfetch emp_cursor into emp_record;--每取出一条数据，指针自动下移exit when(emp_cursor%notfound);--最后次取数据失败dbms_output.put_line(emp_record.empno|| '  ' ||emp_record.ename);end loop;--第四步：关闭游标close emp_cursor;
end;
/--错误例子
declare--第一步：声明游标cursor emp_cursor is select * from scott.emp where rownum<=10; emp_record scott.emp%rowtype;
begin--第二步：打开游标open emp_cursor;--第三步：从游标中取数据loopfetch emp_cursor into emp_record;--每取出一条数据，指针自动下移dbms_output.put_line(emp_record.empno|| '  ' ||emp_record.ename);exit when(emp_cursor%notfound);--最后次取数据失败end loop;--第四步：关闭游标close emp_cursor;
end;
/--使用游标取出emp表总前10人的信息。  whiledeclare--第一步：声明游标cursor emp_cursor is select * from scott.emp where rownum<=10; emp_record scott.emp%rowtype;
begin--第二步：打开游标open emp_cursor;--第三步：从游标中取数据fetch emp_cursor into emp_record;while(emp_cursor%found)loopdbms_output.put_line(emp_record.empno|| '  ' ||emp_record.ename);fetch emp_cursor into emp_record; end loop;--第四步：关闭游标close emp_cursor;
end;
/--使用游标取出emp表总前10人的信息。 for  必须掌握declare--第一步：声明游标cursor emp_cursor is select * from scott.emp where rownum<=10; emp_record scott.emp%rowtype;
beginfor emp_rec in emp_cursor loopdbms_output.put_line(emp_rec.empno|| '  ' ||emp_rec.ename);  end loop;
end;
/--使用游标取出emp表总指定job 和 deptno的员工信息。select * from scott.emp declare--第一步：声明游标cursor emp_cursor(v_job scott.emp.job%type,v_deptno scott.emp.deptno%type) is select * from scott.emp where job=v_job and deptno=v_deptno; emp_record scott.emp%rowtype;
beginfor emp_rec in emp_cursor('CLERK',30) loopdbms_output.put_line(emp_rec.empno|| '  ' ||emp_rec.ename);  end loop;
end;
/--模糊查询select PATINDEX('%abb%','abcaabbeeabb') from dual;select * from scott.emp where regexp_like(ename, '[AS]MITH');--SMITHselect * from scott.emp where ename like 'SMITH';--游标的update操作
--更新指定图书的名字
declarecursor book_cursor is select * from  t_book for update; --v_id t_book.id%type:=v_id;v_name t_book.name%type:=&v_name;
beginfor book_rec in book_cursor loopif(book_rec.tid=1)  then update t_book set name=v_name where current of book_cursor;end if;end loop;end;
/   --隐式游标（了解）
--更新指定图书的名字，如果该图书没有找到，则打印”查无此图书”。
declarev_name t_book.name%type:=&v_name;v_id t_book.id%type:=&v_id;beginupdate t_book set  name=v_name where id=v_id;if(sql%found) thendbms_output.put_line('修改成功： '||v_id||' '||v_name);elsif(sql%notfound) thendbms_output.put_line('没有指定id的图书 ');end if;
end;
/   -------------存储过程
create or replace procedure p1
asv_name t_book.name%type:='言情';v_id t_book.id%type:=1;
beginupdate t_book set name=v_name where id =v_id;if(sql%found) thendbms_output.put_line('修改成功');end if;
end;
/--调用存储过程
exec p1;select * from t_book;beginp1;
end;
/--带参数的存储过程
--求1...N的和 （N为入参）
create or replace procedure p2(v_number in number)
asv_sum number:=0;v_i number:=0;
beginfor v_i in 0..v_number loopv_sum:=v_sum+v_i;end loop; dbms_output.put_line(v_sum);
end;--调用
beginp2(100);
end;
/--带参数的存储过程
--求1...N的和 （v_number为入参,v_sum为出参）
create or replace procedure p3(v_number in number,v_sum out number)
as     beginv_sum :=0;for v_i in 0..v_number loopv_sum:=v_sum+v_i;end loop; dbms_output.put_line('存储过程中打印：'||v_sum);
end;--调用
declarev_sum number;
beginp3(100,v_sum);dbms_output.put_line('调用打印：'||v_sum);
end;
/--函数 无参
create or replace function my_funreturn date
asv_date date;
beginselect sysdate into v_date from dual;return v_date;
end;
/--调用
select my_fun() from dual;
---
declarev_date date;
beginv_date:=my_fun();dbms_output.put_line(v_date);
end;
/--函数 带参数
--根据id查询出图书名字
create or replace function getName(v_id t_book.id%type)return t_book.name%type
asv_name t_book.name%type;beginselect name into v_name from t_book where id = v_id;return v_name;
end;
/--调用declare v_name t_book.name%type;
beginv_name:=getName(2);dbms_output.put_line(v_name);
end;
/--触发器
create table book_log(username varchar2(10),action varchar2(10),adate  date
) select * from a;create or replace trigger trigger_bookafter insert or update or delete on scott.a
beginif inserting theninsert into book_log values (user,'insert',sysdate); elsif updating theninsert into book_log values (user,'update',sysdate); elsif deleting theninsert into book_log values (user,'delete',sysdate); end if;
end;
/
--测试
select * from a;
select * from book_log;insert into a values (8,'龙磊的铃声'); update a set name='龙磊' where id = 8;delete from a set name='龙磊' where id = 8;--行触发器create or replace trigger trigger_bookafter insert or update or delete on scott.a for each row
beginif inserting theninsert into book_log values (user,'insert',sysdate); elsif updating theninsert into book_log values (user,'update',sysdate); elsif deleting theninsert into book_log values (user,'delete',sysdate); end if;
end;
/
--update a set name=name||'2';delete from book_log;select * from book_log;select * from a;select * from emp;
--异常处理（了解）declarev_empno scott.emp.empno%type:=&v_empno;v_emp_rec emp%rowtype;
beginselect * into v_emp_rec from scott.emp  where scott.emp.empno=v_empno;dbms_output.put_line(v_emp_rec.empno||' '||v_emp_rec.ename);exceptionwhen no_data_found then dbms_output.put_line('没有此编号的员工 ');
end;
/declarev_deptno scott.emp.deptno%type:=&v_deptno;v_emp_rec emp%rowtype;
beginselect * into v_emp_rec from scott.emp  where scott.emp.deptno=v_deptno;dbms_output.put_line(v_emp_rec.empno||' '||v_emp_rec.ename);exceptionwhen no_data_found then dbms_output.put_line('没有此编号的员工 ');when too_many_rows then dbms_output.put_line('select 语句返回了多行数据 ');
end;

with e as 用法：

其实就是把一大堆重复用到的sql语句放在with as里面，取一个别名，后面的查询就可以用它，这样对于大批量的sql语句起到一个优化的作用，而且清楚明了。with e as (select * from smc_sql )
select * from e
where e.id=2;with as优点
增加了sql的易读性，如果构造了多个子查询，结构会更清晰；
更重要的是：“一次分析，多次使用”，这也是为什么会提供性能的地方，达到了“少读”的目标