2023年马士兵oracle笔记.doc

第一课：客户端
1. Sql Plus(客户端），命令行直接输入：sqlplus，然后按提醒输入用户名，密码。
2. 从开始程序运营:sqlplus，是图形版的sqlplus.
3. http://localhost:5560/isqlplus

Toad：管理， PlSql Developer:

第二课：更改用户
1. sqlplus sys/bjsxt as sysdba
2. alter user scott account unlock;(解锁)

第三课：table structure

1. 描述某一张表：desc 表名
2. select * from 表名
第四课：select 语句：

1.计算数据可以用空表：比如：.select 2*3 from dual

2.select ename,sal*12 annual_sal from emp;与select ename,sal*12 "annual sal" from emp;区别，加双引号保持原大小写。不加全变大写。

3. select ename "abcd" 假如连接字符串中具有单引号，用两个单引号代替一个单引号。

第五课：distinct
select deptno from emp;
select distinct deptno from emp;

select distinct deptno from emp;
select distinct deptno ,job from emp
去掉deptno,job两者组合的反复。更多的项，就是这么多项的组合的不反复组合。
第六课：Where
select * from emp where deptno =10;
select * from emp where deptno <>10;不等于10
select * from emp where ename ='bike';
select ename,sal from emp where sal between 800 and 1500 (>=800 and <=1500)
空值解决:
select ename,sal,comm from emp where comm is (not) null;

select ename,sal,comm from emp where ename ( not)in ('smith','king','abc');
select ename from emp where ename like '_A%';_代表一个字母,%代表0个或多个字母. 假如查询%
可用转义字符.\%. 还可以用escape '$'比如:select ename from emp where ename like '%$a%' escape '$';

第七课: orderby

select * from dept;
select * from dept order by dept desc;(默认:asc)
select ename,sal,deptno from emp order by deptno asc,ename desc;

第八课: sql function1:
select ename,sal*12 annual_sal from emp
where ename not like '_A%' and sal>800
order by sal desc;

select lower(ename) from emp;

select ename from emp
where lower(ename) like '_a%';等同于
select ename from emp where ename like '_a%' or ename like '_A%';

select substr(ename,2,3) from emp;从第二字符截,一共截三个字符.
select chr(65) from dual 结果为:A
select ascii('a') from dual 结果为:65
select round(23.652,1) from dual; 结果为: 23.7
select round(23.652,-1) from dual; 20

select to_char(sal,'$99_999_999') from emp;
select to_char(sal,'L99_999_999') from emp;人民币符号,L:代表本地符号

这个需要掌握牢:
select birthdate from emp;
显示为:
BIRTHDATE
----------------
17-12月-80
----------------

改为:
select to_char(birthdate,'YYYY-MM-DD HH:MI:SS') from emp;

显示:

BIRTHDATE
-------------------
198012-17 12:00:00
-------------------

select to_char(sysdate,'YYYY-MM-DD HH24:MI:SS') from dual; //也可以改为:HH12
TO_CHAR(SYSDATE,'YY
-------------------
2023-02-25 14:46:14

to_date函数:
select ename,birthdate from emp where birthdate > to_date('1981-2-20 12:34:56','YYYY-MM-DD HH24:MI:SS');
假如直接写 birthdate>'1981-2-20 12:34:56'会出现格式不匹配,由于表中的格式为: DD-MM月-YY.

select sal from emp where sal>888.88 无错.但
select sal from emp where sal>$1,250,00;
会出现无效字符错误.
改为:
select sal from emp where sal>to_number('$1.250.00','$9,999,99');

把空值改为0
select ename,sal*12+nvl(comm,0) from emp;
这样可以防止comm为空时,sal*12相加也为空的情况.

第九课: Group function 组函数
max,min,avg ,count,sum函数

select to_char(avg(sal),'99999999,99') from emp;

select round(avg(sal),2) from emp;
结果:2073.21

select count(*) from emp where deptno=10;
select count(ename) from emp where deptno=10; count某个字段,假如这个字段不为空就算一个.
select count(distinct deptno) from emp;
select sum(sal) from emp;

第十课: Group by语句

需求:现在想求,求每个部门的平均薪水.
select avg(sal) from emp group by deptno;
select deptno avg(sal) from emp group by deptno;

select deptno,job,max(sal) from emp group by deptno,job;

求薪水值最高的人的名字.

select ename,max(sal) from emp;犯错,由于max只有一个值,但等于max值的人也许好几个,不能匹配.
应如下求:
select ename from emp where sal=(select max(sal) from emp);

Group by语句应注意,

出现在select中的字段,假如没出现在组函数中,必须出现在Group by语句中.

第十一课: Having 对分组结果筛选

Where是对单条纪录进行筛选,Having是对分组结果进行筛选.

select avg(sal),deptno from emp
group by deptno
having avg(sal)>2023;

查询工资大于1200雇员,按部门编号进行分组,分组后平均薪水大于1500,按工薪倒充排列.
select * from emp
where sal>1200
group by deptno
having avg(sal)>1500
order by avg(sal) desc;

第十二课:字查询

谁挣的钱最多(谁:这个人的名字, 钱最多)

select 语句中嵌套select 语句,可以在where,from后.

问那些人工资,在平均工资之上.

select ename,sal from emp where sal>(select avg(sal) from emp);

查找每个部门挣钱最多的那个人的名字.
select ename ,deptno from emp where sal in(select max(sal) from ename group by deptno) 查询会多值.

应当如下:

select max(sal),deptno from emp group by deptno;当成一个表.语句如下:
select ename, sal from emp join(select max(sal) max_sal,deptno from emp group
by deptno) t on(emp.sal=t.max_sal and emp.deptno=t.deptno);

每个部门的平均薪水的等级.
分析:一方面求平均薪水(当成表),把平均薪水和此外一张表连接.

第十四课:self_table_connection

把某个人的名字以及他的经理人的名字求出来(经理人及这个人在表中同处一行)

分析:一方面求出这个人的名字,取他的编号,然后从另一张表与其相相应编号,然后找到经理的名字.

select e1.ename ,e2.ename from emp e1,emp e2 where e1.mgr= e2.empno.

empno编号和MGR都是编号.

第十15课: SQL1999_table_connections

select ename,dname,grade from emp e,dept d, sqlgrade s
where e.deptno = d.deptno and e.sql between s.losal and s.hisal and
job<>'CLERK';

有没有办法把过滤条件和连接条件分开来? 出于这样考虑,Sql1999标准推出来了.有许多人用的还是
旧的语法,所以得看懂这种语句.

select ename,dname from emp,dept;(旧标准).
select ename,dname from emp cross join dept;(1999标准)

select ename,dname from emp,dept where emp.deptno=dept.deptno (旧)
select ename,dname from emp join dept on(emp.deptno = dept.deptno); 1999标准.没有Where语句.
select ename,dname from emp join dept using(deptno);等同上句,但不推荐使用.

select ename,grade from emp e join salgrade s on(e.sal between s.losal and s.hisal);
join 连接语句, on过滤条件。连接，条件一眼分开。假如用Where语句较长时，连接语句和过滤语句混在一起。

三张表连接：
slect ename,dname, grade from
emp e join dept d on(e.deptno=d.deptno)
join salgrade s on(e.sal between s.losal and s.hisal)
where ename not like '_A%';
把每张表连接 条件不混在一起，然后数据过滤条件所有区分开来。读起来更清楚，更容易懂一点。

select e1.ename,e2.ename from emp e1 join emp e2 on(e1.mgr = e2.emptno);

左外连接：会把左边这张表多余数据显示出来。
select e1.ename,e2,ename from emp e1 left join emp e2 on(e1.mgr =e2.empno);left 后可加outer
右外连接：
select ename,dname from emp e right outer join dept d on(e.deptno =d.deptno); outer可以取掉。

即把左边多余数据，也把右边多余数据拿出来，全外连接。
select ename,dname from emp e full join dept d on(e.deptno =d.deptno);

16-23 课：求部门平均薪水的等级

A.求部门平均薪水的等级。

select deptno,avg_sal,grade from
(select deptno,avg(sal) avg_sal from emp group by deptno)t
join salgrade s on(t.avg_sal between s.losal and s.hisal)

B.求部门平均的薪水等级
select deptno,avg(grade) from
(select deptno,ename, grade from emp join salgrade s on(emp.sal between s.losal and
s.hisal)) t
group by deptno

C.那些人是经理
select ename from emp where empno in(select mgr from emp);
select ename from emp where empno in(select distinct mgr from emp);

D.不准用组函数，求薪水的最高值（面试题）

select distinct sal from emp where sal not in(
select distinct e1.sal from emp e1 join emp e2 on (e1.sal
F.平均薪水最高的部门名称
select dname from dept where deptno=
(
select deptno from
(select avg(sal)avg_sal,deptno from emp group by deptno)
where avg_sal=
(select max(avg_sal)from
(select avg(sal) avg_sal,deptno from emp group by deptno)
)
)

G.求平均薪水的等级最低的部门的部门名称

组函数嵌套
如：平均薪水最高的部门编号，可以E.更简朴的方法如下：
select deptno,avg_sal from
(select avg(sal) avg_sal,deptno from emp group by deptno)
where avg_sal =
(select max(avg(sal)) from emp group by deptno)

组函数最多嵌套两层

分析：
一方面求
1.平均薪水： select avg(sal) from group by deptno;

2.平均薪水等级： 把平均薪水当做一张表，需要和此外一张表连接salgrade
select deptno,grade avg_sal from
( select deptno,avg(sal) avg_sal from emp group by deptno) t
join salgrade s on(t.avg_sal between s.losal and s.hisal)

上面结果又可当成一张表。

DEPTNO GRADE AVG_SAL
-------- ------- ----------
30 3 1566.66667
20 4 2175
10 4 2916.66667

3.求上表平均等级最低值

select min(grade) from
(
select deptno,grade,avg_sal from
(select deptno,avg(sal) avg_sal from emp group by deptno)t
join salgrade s on(t.avg_sal between s.losal and s.hisa)
)

4.把最低值相应的2结果的那张表的相应那张表的deptno, 然后把2相应的表和此外一张表做连接。

select dname ,deptno,grade,avg_sal from
(
select deptno,grade,avg_sal from
(select deptno,avg(sal) avg_sal from emp group by deptno)t
join salgrade s on(t.avg_sal between s.losal and s.hisal)
) t1
join dept on (t1.deptno = dept.deptno)
where t1.grade =
(
select deptno,grade,avg_sal from
(select deptno,avg(sal) avg_sal from emp group by deptno) t
join salgrade s on(t.avg_sal between s.losal and s.hisal)
)
)
结果如下：

DNAME DEPTNO GRADE AVG_SAL
-------- ------- -------- --------
SALES 30 3 1566.6667

H: 视图（视图就是一张表，一个字查询）

G中语句有反复，可以用视图来简化。
conn sys/bjsxt as sysdba;
grant create table,create view to scott;
conn scott/tiger
创建视图：
create view v$_dept_avg-sal_info as
select deptno,grade,avg_sal from
( select deptno,avg(sal) avg_sal from emp group by deptno)t
join salgrade s on 9t.avg_sal between s.losal and s.hisal)

然后
select * from v$_dept_avg-sal_info

结果如下：
DEPTNO GRADE AVG_SAL
-------- ------- ----------
30 3 1566.66667
20 4 2175
10 4 2916.66667

然后G中查询可以简化成：
select dname,t1.deptno,grade,avg_sal from
v$_dept_avg-sal_info t1
join dept on9t1.deptno =dept.deptno)
where t1.grade=
(
select min(grade) from v$_dept_avg-sal_info t1
)

--变量声明，使用%type属性
declare
v_empno number(4);
v_empno2 emp.empno%type;
v_empno3 v_empno2%type;
begin
dbms_output.put_line('test');
end;

--table变量类型(数组)
declare
type type_table_emp_empno is table of emp.empno%type index by binary_integer;
v_empnos type_table_emp_empno;
begin
v_empnos(0) := 7369;
v_empnos(2) := 7839;
v_empnos(-1) := 9999;
dbms_output.put_line(v_empnos(-1));
end;

--record变量类型（近似java中的类）
declare
type type_record_dept is record
(
deptno dept.deptno%type,
dname dept.dname%type,
loc dept.loc%type
);
v_temp type_record_dept;
begin
v_temp.deptno := 50;
v_temp.dname := 'aaa';
v_temp.loc := 'bj';
dbms_output.put_line(v_temp.deptno || ' ' || v_temp.dname);
end;

--使用%rowtype声明record变量
declare
v_temp dept%rowtype;
begin
v_temp.deptno := 50;
v_temp.dname := 'aaa';
v_temp.loc := 'bj';
dbms_output.put_line(v_temp.deptno || ' ' || v_temp.dname);
end;

--SQL语句的运用
--select语句
declare
v_name emp.ename%type;
v_sal emp.sal%type;
begin
select ename, sal into v_name, v_sal from emp where empno = 7369;
dbms_output.put_line(v_name || ' ' || v_sal);
end;

declare
v_emp emp%rowtype;
begin
select * into v_emp from emp where empno = 7369;
dbms_output.put_line(v_emp.ename);
end;

--insert语句

declare
v_deptno dept.deptno%type := 50;
v_dname dept.dname%type := 'aaa';
v_loc dept.loc%type := 'bj';
begin
insert into dept2 values(v_deptno, v_dname, v_loc);
commit;
end;

declare
v_deptno emp2.deptno%type := 10;
v_count number;
begin
--update emp2 set sal = sal/2 where deptno = v_deptno;
--select deptno into v_deptno from emp2 where empno = 7369;
select count(*) into v_count from emp2;
dbms_output.put_line(sql%rowcount || '条记录被影响');
commit;
end;

DDL语句
begin
execute immediate 'create table t (nnn varchar2(20) default ''aaa'')';
end;

--if语句
取出7369的薪水，假如<1200，输出'low'，假如<2023输出'middle'，否则'high'

declare
v_sal emp.sal%type;
begin
select sal into v_sal from emp
where empno = 7369;
if (v_sal < 1200) then
dbms_output.put_line('low');
elsif (v_sal < 2023) then
dbms_output.put_line('middle');
else
dbms_output.put_line('high');
end if;
end;

--练习

--循环
declare
i binary_integer := 1;
begin
loop
dbms_output.put_line(i);
i := i + 1;
exit when (i >= 11);
end loop;
end;
---------
declare
j binary_integer := 1;
begin
while j < 11 loop
dbms_output.put_line(j);
j := j + 1;
end loop;
end;

-----------
begin
for k in 1..10 loop
dbms_output.put_line(k);
end loop;

for k in reverse 1..10 loop
dbms_output.put_line(k);
end loop;
end;

--错误解决
declare
v_temp number(4);
begin
select empno into v_temp from emp where empno = 10;
exception
when too_many_rows then
dbms_output.put_line('太多纪录了');
when others then
dbms_output.put_line('error');
end;

----------

declare
v_temp number(4);
begin
select empno into v_temp from emp where empno = 2222;
exception
when no_data_found then
dbms_output.put_line('没有数据');
end;

---------
--创建事件