前言
这是我上学期Oracle期末考试前整理的一些资料，今天调整了部分格式后分享出来。希望能帮到要考Oracle（以写SQL语句为主的考试）的小🔥伴儿们~
一、简介
1. 登录
结尾无分号
sqlplus sys/11111 as sysdba
-
切换用户（关键词：
Connect）connect scott/tiger -
用户表中可使用的磁盘空间大小（关键词：
Quota）[了解]create user linda identified by 111111 default tablespace users quota 10M on users; -
用户默认密码已过期，用户登录前需修改（关键词：
password expire）[了解]create user linda identified by 111111 password expire;
2. 授权
- 建立会话（登录）系统权限：grant create session to linda;
- 创建数据表的系统权限：grant create table to linda;
- 授权和数据库建立连接的角色：grant connect to linda;
3. 修改
关键词：Alter
-
修改密码
alter user linda indentified by 111112;
4. 启用与禁用
alter user linda account lock;
alter user linda account unlock;
5. 删除
若用户方案中存在对象，则需要用cascade
drop user linda cascade;
6. 索引、序列、角色、用户
-
索引是表的一个微型拷贝
create role hr_clerk identified by password;注：identified by后为密码
create user user_name identified by password;
二、表
1. 创建表
create table haha
(deptno number(2),
dname varchar2(14),
loc varchar2(13));
查看表信息：describe haha
1.1 子查询创建表
create table dept30
as
select empno, ename, sal*12 annsal
from emp
where deptno=30;
1.2 定义约束！！！
关键词：constraint
- 非空：
not null
create table haha
(empno number(4),
ename varchar2(10),
deptno number(7, 2) not null,
constraint emp_empno_pk primary key (empno));
-
唯一码约束：
unique -
主键约束：
primary key -
外键约束：
foreign key, references -
Check约束：
check
create table haha
(empno number(2),
ename varchar2(10) not null,
job varchar2(9),
sal number(7,2),
comm number(7,2),
mgr number(4),
hiredate date,
deptno number(7,2) not null,
constraint haha_ename_uk unique (ename),
constraint haha_empno_pk primary key (empno),
constraint haha_deptno_fk foreign key (deptno)
references dept (deptno)
constraint haha_deptno_ck check
(deptno between 10 and 99));
Q：number(7,2)含义？
A：7位有效数字，其中包含2位小数
1.3 管理约束
-
增加
alter table haha add constraint haha_mgr_fk foreign key (mgr) references emp (empno); -
删除
alter table haha drop constraint haha_mgr_fk;alter table haha drop primary key cascade; -
禁用
alter table haha enable constraint haha_empno_pk;alter table haha disable constraint haha_empno_pk cascade;
2. 更改表
关键词：alter, add, modify, drop column
alter table haha
add (job varchar2(9));
alter table haha
modify (job varchar2(10));
alter table haha
drop column job;
alter table haha
drop unused column;
2.1 更改表名称
关键词：rename ... to ...
rename haha to fafa;
3. 删除表
drop table haha;
若删除的表中包含有被其它表外部码引用的码，并希望删除表的同时删除其它表中的相关外部码约束，则需要加cascade语句
drop table haha cascade constraints;
4. 截断表
关键词：truncate
truncate table fafa;
5. 注释表
关键词：comment
comment on table emp is ‘Employee Information’;
三、视图
1. 创建视图
-
关键词：create view … as …
create view emp_view as select empno, ename, sal from emp;scott账户下创建视图会显示权限不足。解决方法如下
-
以system/pw登录oracle;
-
输入
grant create any view to scott; -
重新登录scott账户，即可创建视图
2. 重定义视图
-
关键词：create or replace view …
create or replace view emp_view as select empno, ename, sal, loc from emp, dept where emp.deptno = dept.deptno;
3. 删除视图
-
关键词：
dropdrop view emp_view;
4. 更改视图
create or replace view empvu10 (employee_number, employee_name, job_title)
as
select empno, ename, job
from emp
where deptno = 10;
思考：如何修改视图中某列的名称？
四、DML
1. Insert！！！
关键词：insert into… values…
注意括号！
insert into emp (empno, ename, job, mgr, hiredate, sal, comm, deptno)
values (9000, 'GREEN', 'SALESMAN', 7782, sysdate, 2000, null, 10);
1.1 插入多行数据
insert into salesman (id, name, job, hiredate)
select empno, ename, job, hiredate
from emp
where job = 'SALESMAN';
2. Update！！！
关键词：update… set… where…
update emp
set sal=8000
where ename='Anne';
2.1 更新多列数据
update emp
set (job, deptno) = (select job, deptno
from emp
where empno = 9000)
where empno = 7369;
3. Delete
关键词：delete from… where
delete from dept
where deptno = 50;
五. 查询
1. 消除重复行
关键词：distinct
select distinct deptno
from emp;
2. 比较
注意：is后接NULL或者not NULL，不用来做其它比较，如job = 'SALESMAN’不可将=改为is
-
in(list)[list列中成员匹配]select empno, ename, sal, mgr from emp where mgr in (7902, 7566, 7788)1.1
notselect ename, job from emp where job not in ('CLERK', 'MANAGER', 'ANALYST'); -
like [字符匹配]
%：匹配0或多个字符_：匹配单一字符
select ename from emp where ename like '_A%'; -
is nullselect ename, mgr from emp where mgr is null;
3. 日期相减
- select empno, ename, job, sysdate-hiredate hiredays from emp;
4. 数值转换
- select ename, to_char(sal, ‘$0,999.00’) salary from emp;
5. 空值置换
-
NVL(expr1, expr2)若expr1 = NULL, 返回expr2；否则，返回expr1
select ename, sal, (sal*12) + NVL(comm, 0) annual_sal from emp;
select ename, NVL(to_char(mgr), 'No Manager') status from emp where mgr is null;
-
NVL2(expr1, expr2, expr3)若expr1 = NULL, 返回expr3；否则，返回expr2
select ename, sal, (sal*12) + NVL2(comm, 3000+comm, 3000) annual_sal from emp;
6. 条件表达式！！！
CASE
select ename, job, sal,
case job when 'ANALYST' then 1.10*sal
when 'CLERK' then 1.15*sal
when 'SALESMAN' then 1.20*sal
else sal
end
revised_salary from emp;
DECODE
select ename, job, sal,
decode(job, 'ANALYST', 1.10*sal,
'CLERK', 1.15*sal,
'SALESMAN', 1.20*sal,
sal)
revised_salary from emp;
使用decode计算个税
select ename, job, sal,
decode(sal, sal < 1500, 0.97*sal,
1500 < sal < 4500, 0.9*sal-105,
4500 < sal < 9000, 0.8*sal-555,
sal > 9000, 0.75*sal-1005,
sal)
revised_salary from emp;
7. 连接查询（高级查询）
- 相等连接
- 使用 “=” 连接
select emp.empno, emp.ename, emp.deptno,
dept.deptno, dept.dname, dept.loc
from emp, dept
where emp.deptno=dept.deptno;
-
不相等连接
-
使用
between连接 -
简化
emp表示的方法：在where后用e代替emp
-
select e.ename, e.sal, s.grade
from emp e, salgrade s
where e.sal
between s.losal and s.hisal;
-
外连接！！！
select e.ename, d.deptno, d.dname from emp e, dept d where e.deptno(+) = d.deptno order by e.deptno;- 使用 “(+)” 连接 （在表中加入一个空行与没有直接匹配行的数据经行匹配）
- 完全外部连接
select ename, dname from emp full outer join dept on dept.deptno = emp.deptno;
-
自连接
select w.ename "Worker", m.ename "Manager" from emp w, emp m where w.mgr = m.empno;
8. 递归查询！！！
- 关键词：
Start with,Connect by prior
查询Jones的所有下属员工
SELECT empno, ename, level
FROM emp
START WITH ename = 'JONES'
CONNECT BY PRIOR empno = mgr;
查询Jones的上级员工时将上方SQL最后改为：mgr=empno
可以理解为：查谁谁在前
9. 分组函数
-
avg,max,min,sum在计算时会忽略NULL行；但若数值全为NULL，则计算结果为NULLselect avg(sal), max(sal), sum(sal) from emp where job like 'SALES%';select avg(comm), max(comm), sum(comm) from emp where job like 'SALES%'; -
count-
count(*)所有行数
select count(*) from emp where job = 'SALESMAN'; -
count(expr)：返回非NULL行数
-
-
group by-
分一组
select deptno, SUM(sal) from emp group by deptno; -
分多组
select deptno, job, SUM(sal) from emp group by deptno, job; -
限制选择组 (使用 having)
select deptno, max(sal) from emp group by deptno having max(sal)>1500;在
Where子句中不能直接使用组函数
-
10. 子查询
-
单行子查询
select ename, job from emp where job = (select job from emp where empno = 7369) and sal > (select sal from emp where empno = 7876);总结：子查询select后的项目与操作符前的相同
select deptno, min(sal) from emp group by deptno having min(sal) > (select min(sal) from emp where deptno = 20); -
多行子查询
-
Anyselect empno, ename, job, sal from emp where sal < any (select sal from emp where job = 'CLERK') and job <> 'CLERK'; -
Allselect empno, ename, job, sal from emp where sal < all (select avg(sal) from emp); -
Existsselect e.empno, e.ename from emp e where exists (select 'X' from dept d where e.deptno = d.deptno and d.loc = 'NEW YORK'); -
Inselect e.empno, e.ename, d.deptno from emp e where e.deptno in (select d.deptno from dept d where d.loc = 'NEW YORK');
-
11. 嵌套查询
create or replace view dept_sum_vu
as select d.dname "部门名称", e.minsal "最低工资", e.maxsal "最高工资", e.avgsal "平均工资"
from dept d,
(select deptno, min(sal) minsal, max(sal) maxsal, avg(sal) avgsal
from emp
group by deptno) e
where d.deptno = e.deptno;
六. PL/SQL
1. PL/SQL编程基础
1.1 符号
三种不等于：<> ， != ， ^=
赋值：:=
注释：-- ， /* */
PL/SQL块结构
declare --可选
/* 变量，游标，用户定义异常 */
begin --必须
/* SQL或PL/SQL */
exception --可选
end; --必须
PL/SQL块种类
- 匿名块：Declare… Begin… Exception… End;
- 储存过程：Procedure name is… Begin… Exception… End name;
- 函数：Function name… Return datatype is… Begin…return value; Exception… End name;
1.2 声明变量
- v=varible 变量
- c=constant 常量， 定义常量时必须同时为它赋值，否则会出现错误
- boolean变量的三种值：True, False, Null；boolean一般和and, or, not一起使用
- ‘YYYY/MM/DD HH24:MI:SS’
declare
v_ename varchar2(10);
v_sal number(6,2);
c_tax_rate constant number(3,2) := 5.5;
v_hiredate date;
v_valid boolean not null default false;
1.3 引用
-
%type：定义简单变量
前缀为1.数据库的表.列名，2.先前声明的变量名
v_ename emp.ename%type; v_balance number(7,2); v_min_balace v_balance%type; -
%rowtype：定义记录变量
record_variable [schema.]table_name%rowtype
1.4 转换员工姓名为小写
v_ename := lower(v_ename);
1.5 PL/SQL中的select
declare
v_ename emp.ename%type;
v_empno emp.empno%type;
begin
select ename, empno
into v_ename, v_empno
from emp
where empno = 9000;
dbms_output.put_line(v_ename||' '||v_empno);
end;
DECLARE
v_empRecord emp%ROWTYPE;
BEGIN
-- 从emp表中检索一条记录并存储到v_empRecord记录变量中。
SELECT *
INTO v_empRecord
FROM emp
WHERE empno = 7369;
dbms_output.put_line(v_empRecord.empno||v_empRecord.ename||v_empRecord.sal);
END;
declare
v_sum_sal emp.sal%type;
v_deptno number not null := 10;
begin
select sum(sal) --组函数
into v_sum_sal
from emp
where deptno = v_deptno;
dbms_output.put_line(v_sum_sal);
end;
1.6 PL/SQL中的DML
-
插入
关键点：v_deptno := &no v_dname := '&name’
declare v_deptno dept.deptno%type; v_dname dept.dname%type; begin v_deptno := &no; --表示替代变量，当程序被执行时，系统会提示为其输入值 v_dname := '&name'; --同上 insert into dept (deptno, dname) values (v_deptno, v_dname); end; -
更新
declare v_sal_increase emp.sal%type := 180; begin update emp set sal = sal + v_sal_increase where job = 'SALESMAN'; end; -
删除
declare v_deptno emp.deptno%type := 10; begin delete from emp where deptno = v_deptno; end;
1.7 PL/SQL中的Commit & Rollback
declare
v_sal number(10,2) := &salary;
v_ename varchar2(20) := '&name';
begin
update emp
set sal = v_sal
where ename = v_ename;
commit;
exception
when others then
rollback;
end;
1.8 if
declare
v_sal emp.sal%type;
v_ename emp.ename%type := '&ename';
begin
select sal into v_sal from scott.emp
where lower(ename) = lower(v_ename);
if v_sal < 2000 then
update emp
set sal := v_sal + 200
where lower(ename) = lower(v_ename);
end if;
end;
注意处理null的方法
declare
v_comm emp.comm%type;
v_empno emp.empno%type := &no;
begin
select nvl(comm, 0) into v_comm from scott.emp
where empno = v_empno;
if v_comm <> 0 then
update emp
set comm = v_comm + 200
where empno = v_empno;
else
update emp
set comm = 100
where empno = v_empno;
end if;
end;
思考: select… into…含义？
1.9 loop/for
declare
v_num number(2) := #
v_pro number(20) := 1;
i number(2) := 1;
begin
if v_num = 0 then
v_pro := 1;
else
loop
v_pro := v_pro*i;
i := i+1;
exit when i>v_num;
end loop;
end if;
dbms_output.put_line('num:'||v_num||' factorial:'||v_pro);
end;
- for循环中不声明计数器变量；计数器不能在loop循环体外部定义
declare
v_num number(2) := #
v_pro number(20) := 1;
begin
if v_num = 0 then
v_pro := 1;
else
for i in 1..v_num loop
v_pro := v_pro*i;
end loop;
end if;
dbms_output.put_line('num:'||v_num||' factorial'||v_pro);
end;
1.10 游标Cursor
- 定义的sql语句必须只包含select语句，且不能使用
insert，update，delete等关键字 - 显示游标应用场景：select语句返回零或多于一行
- 隐式游标应用场景：select语句只返回一行
-
声明游标 (不能包含into语句)
关键词：cursor… is…
declare cursor c1 is select empno, ename from emp; cursor c2 is select * from dept where deptno = 10; ... -
从游标中提取数据
- 反复使用fetch来提取每一行数据
declare cursor c1 is select * from emp; emp_rec emp%rowtype; --定义一个和表结构完全一致的记录变量 begin open c1; fetch c1 into emp_rec; dbms_output.put_line('姓名是：'||emp_rec.ename||' 工作是：'||emp_rec.job||' 工资是：'||emp_rec.sal); close c1; end; -
游标提取basic loop
declare cursor emp_cursor is select ename, sal from emp where deptno=10; emp_record emp%rowtype; begin open emp_cursor; loop fetch emp_cursor into emp_record.ename, emp_record.sal; exit when emp_cursor%notfound; dbms_output.put_line('ename: '||emp_record.ename||' sal:'||emp_record.sal); end loop; dbms_output.put_line('row count: '||emp_cursor%rowcount); close emp_cursor; end; -
游标提取while loop
declare cursor emp_c is select ename, sal from emp where deptno=10; emp_rec emp%rowtype; begin open emp_c; fetch emp_c into emp_rec.ename, emp_rec.sal; while emp_c%found loop dbms_ouput.put_line('ename: '||emp_rec.ename||' sal: '||emp_rec.sal); end loop; dbms_output.put_line('row count: '||emp_c%rowcount); close emp_c; end; -
游标提取for loop
- for前系统自动open游标，for中系统自动fetch游标，for后系统自动close游标
- for循环中的循环控制变量不需要事先定义
declare cursor emp_c is select ename, sal from emp where deptno=10; begin for emp_rec in emp_c loop dbms_output.put_line('ename: '||emp_rec.ename||' sal: '||emp_rec.sal); end loop; end;declare cursor c1 is select * from emp order by sal desc; begin for rec in c1 loop if c1%rowcount <= 5 then dbms_ouput.put_line('ename: '||rec.ename||' sal: '||rec.sal); else exit; end if; end loop; end;
2. PL/SQL程序设计
2.1 触发器
create or replace trigger secure_emp
before insert on emp
begin
if(to_char(sysdate, 'DY')in('星期六','星期天'))
or(to_char(sysdate, 'HH24:MI')not between '08:00' and '18:00')
then
if deleting then
raise_application_error(-20502, 'You may delete from emp table only during business hours.');
elsif inserting then
raise_application_error(-20500, 'You may insert into emp table only during business hours.');
elsif updating('SAL') then
raise_application_error(-20503, 'You may update sal only during business hours.');
else
raise_application_error(-20504, 'You may update emp table only during normal hours.');
end if;
end if;
end
- 行级触发器：使用
:old和:new
2.2 过程函数
-
过程与匿名块相比
- 无declare关键字
- 再end后可以加过程名，作为定义结束的标志
- 定义完成后需要调用才能执行过程内部代码
create or replace procedure display_time is begin dbms_output.put_line(systimestamp); end display_time;调用：call display_time();
create or replace procedure query_emp
(p_id in emp.empno%type,
p_name out emp.ename%type,
p_salary out emp.sal%type,
p_comm out emp.comm%type)
is
begin
select ename, sal, comm
into p_name, p_salary, p_comm
from emp
where empno = p_id;
end query_emp;
create or replace function select_sal_name
(v_no in scott.emp.empno%type,
v_sal out scott.emp.sal%type,
v_name out scott.emp.ename%type
)
return number
is
v_result number;
begin
select sal, ename into v_sal, v_name
from emp
where empno = v_no;
return v_result;
exception
when NO_DATA_FOUND then
dbms_output.put_line('无符合要求的记录')；
v_result := 0;
v_name := '';
end;
复习结束
那么…
与君👉🏻歌一曲👈🏻，请君为我倾耳听~
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