细数你应该修炼的Oracle基本功
http://database.51cto.com 2010-09-2608:56 yuexingtian Chinaunix
摘要：Oracle数据库的基本功，主要涉及一些小算法，比如求部门中谁的薪水最高，谁是经理等等。希望能满足那些苦苦找寻正确解决方法的DBA们。
标签：Oracle
以下的文章，主要为大家在实际工作中提供一种解决方法。
---用户名：scott
---密 码：tiger
---*********Oracle表连接与子查询示例************
---求部门中哪些人的薪水最高
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);
---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);
---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;
---雇员中哪些人是经理人
select ename from emp where empno in (select distinct mgr from emp);
---不用组函数，求薪水的最高值
select sal from emp where sal not in
(select distinct e1.sal from emp e1 join emp e2 on (e1.sal < e2.sal))；
---用组函数，求薪水的最高值
select max(sal) from emp；
---求平均薪水最高的部门的部门编号
select deptno , avg_sal from
(select avg(sal) avg_sal,deptno from emp group by deptno) t
where avg_sal =
(select max(avg_sal) from (select avg(sal) avg_sal,deptno from emp group by deptno) t)；
----组函数嵌套的写法
select deptno , avg_sal from
(select avg(sal) avg_sal,deptno from emp group by deptno) t
where avg_sal =
(select max(avg(sal)) from emp group by deptno)；
---求平均薪水最高的部门的名称
select dname from dept
where deptno =
(
select deptno from
(select avg(sal) avg_sal,deptno from emp group by deptno) t
where avg_sal =
(select max(avg_sal) from (select avg(sal) avg_sal,deptno from emp group by deptno) t)
)；
---求部门平均薪水
1. select avg(sal) avg_sal,deptno from emp group by deptno
---求平均薪水的等级最低的部门的部门名称
select min(avg_sal) from
(
select avg(sal) avg_sal,deptno from emp group by deptno
)
--平均工资的最小值
select avg_sal,deptno from
(select avg(sal) avg_sal,deptno from emp group by deptno) t
where avg_sal =
(
select min(avg_sal) from
(
select avg(sal) avg_sal,deptno from emp group by deptno
)
)
--平均工资的最小值及部门编号
select t.avg_sal,t.deptno,s.grade from
(select avg(sal) avg_sal,deptno from emp group by deptno) t
join salgrade s on (t.avg_sal between s.losal and s.hisal)
where avg_sal =
(
select min(avg_sal) from
(
select avg(sal) avg_sal,deptno from emp group by deptno
)
)
--平均工资的最小值及部门编号和工资等级
select d.dname,t.avg_sal,t.deptno,s.grade from
(select avg(sal) avg_sal,deptno from emp group by deptno) t
join salgrade s on (t.avg_sal between s.losal and s.hisal)
join dept d on (t.deptno = d.deptno)
where avg_sal =
(
select min(avg_sal) from
(
select avg(sal) avg_sal,deptno from emp group by deptno
)
)
--平均工资的最小值及部门编号和工资等级及部门名称
----Another 按照题意的写法
select t1.deptno,t1.avg_sal,grade,d.dname from
(
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)
) t1
join dept d on (t1.deptno = d.deptno)
where grade =
(
select min(grade) from
(
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)
)
);
---创建视图或者表，如果没有权限
conn sys/sys as sysdba;
--已连接。
grant create table, create view to scott;
--授权成功。
---创建视图
create view v$_dept_avg_sal_info as
select deptno,avg_sal,grade from
(select deptno,avg(sal) avg_sal from emp group by deptno) t
join salgrade s on (t.avg_sal between s.losal and s.hisal);
--视图已建立。
---创建这个v$_dept_avg_sal_info视图可以简化上面那个查询的重复代码
select t1.deptno,t1.avg_sal,grade,d.dname from
v$_dept_avg_sal_info t1
join dept d on (t1.deptno = d.deptno)
where grade =
(
select min(grade) from
v$_dept_avg_sal_info
);
---求比普通员工的最高薪水还要高的经理的名称
select max(sal) from emp where empno not in
(select distinct mgr from emp where mgr is not null);
--普通员工的最高薪水
select ename from emp
where empno in (select distinct mgr from emp where mgr is not null)
and sal >
(
select max(sal) from emp where empno not in(select distinct mgr from emp where mgr is not null)
);
--普通员工的最高薪水还要高的经理的名称
--- Oracle 联机归档日志 备份方式
---求薪水最高的第6名到第10名雇员(rownum)
select ename,sal from
(select ename,sal,rownum r from
(
select ename, sal from emp order by sal desc
)
) where r>=6 and r<=10;
---五种约束条件
create table stu
(
id number(2),
name varchar2(20) constraint stu_name_nn not null,--非空约束
sex number(2),
age number(3),
sdate date,
grade number(3) default 1,
class number(3),
email varchar2(50),
constraint stu_name_email_uin unique(name,email)--唯一主键
) ;
insert into stu(name,email) values('','tianyuexing@163.com')
--ORA-01400: 无法将 NULL 插入 ("SCOTT"."STU"."NAME")
insert into stu(name,email) values('tianyuexing','tianyuexing@163.com');
insert into stu(name,email) values('tianyuexing','tianyuexing@163.com');
--ORA-00001: 违反唯一约束条件 (SCOTT.STU_NAME_EMAIL_UIN)
---PL/SQL 一个简单的存储过程 分为四块1.声明declare2.begin 3.exception 4.end
set serveroutput on;
declare
v_num number :=0;
begin
v_num :=2/v_num;
dbms_output.put_line(v_num);
exception
when others then
dbms_output.put_line('error');
end;
---%type 变量声明的好处。
declare
v_empno2 emp.empno%type;
begin
dbms_output.put_line('test');
end;
---Table 变量类型
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) := 2999;
v_empnos(1) := 2434;
v_empnos(-1) := 8989;
dbms_output.put_line(v_empnos(-1));
end;
---Record 变量类型
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 := 20;
v_temp.dname := 'tianyuexing';
v_temp.loc := 'qhd';
dbms_output.put_line(v_temp.dname || ' ' ||v_temp.loc);
end;
---使用 %rowtype声明record变量
declare
v_temp dept%rowtype;
begin
v_temp.deptno := 20;
v_temp.dname := 'yuexingtian';
v_temp.loc := 'qhd';
dbms_output.put_line(v_temp.dname || ' ' ||v_temp.loc);
end;
---SQL语句的运用
declare
v_ename emp.ename%type;
v_sal emp.sal%type;
begin
select ename,sal into v_ename,v_sal from emp where empno = 7369;
dbms_output.put_line(v_ename ||' '||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 :='yuexingtian';
v_loc dept.loc%type := '秦皇岛';
begin
insert into dept2 values (v_deptno,v_dname,v_loc);
commit;
end;
---sql%rowcount 多少条记录被影响
declare
v_deptno emp2.deptno%type := 10;
v_count number;
begin
update emp2 set sal = sal/2 where deptno = v_deptno;
dbms_output.put_line(sql%rowcount ||'条记录被影响');
end;
--create语句
begin
execute immediate 'create table T (nnn varchar2(20) default ''yuexingtian'')';
end;
---if语句，取出7369的薪水，如果<1200,则输出'low',如果<2000则输出'middle',否则输出'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 < 2000) then
dbms_output.put_line('middle');
else
dbms_output.put_line('high');
end if;
end;
---循环 loop (相当于do while)
declare
i binary_integer := 1;
begin
loop
dbms_output.put_line(i);
i := i+1;
exit when (i>=11);
end loop;
end;
---when ……loop （相当于while）
declare
j binary_integer := 1;
begin
while j<11 loop
dbms_output.put_line(j);
j := j+1;
end loop;
end;
---for ...in... loop
begin
for k in 1..10 loop
dbms_output.put_line(k);
end loop;
for k in reverse 1..10 loop --逆序
dbms_output.put_line(k);
end loop;
end;
--- 异常处理
declare
v_temp number(4);
begin
select empno into v_temp from emp where deptno = 10;
exception
when too_many_rows then --多条记录的异常
dbms_output.put_line('记录太多了');
when others then
dbms_output.put_line('error');
end;
declare
v_temp number(4);
begin
select empno into v_temp from emp where empno = 4444;
exception
when no_data_found then
dbms_output.put_line('没有数据');
end;
---记录数据库错误信息的errorlog
create table errorlog
(
id number primary key,
errcode number,
errmsg varchar2(1024),
errdate date
);
create sequence seq_errorlog_id start with 1 increment by 1; --创建递增序列
--PL/SQL
declare
v_deptno dept.deptno%type :=10;
v_errcode number;
v_errmsg varchar2(1024);
begin
delete from dept where deptno = v_deptno;
commit;
exception
when others then
rollback;
v_errcode := SQLCODE;
v_errmsg := SQLERRM;
insert into errorlog values (seq_errorlog_id.nextval,v_errcode,v_errmsg,sysdate);
commit;
end;
select to_char(errdate,'YYYY-MM-DD HH24:MI:ss') from errorlog; ---具体的出错时间。
---游标
declare
cursor c is
select * from emp;
v_emp c%rowtype;
begin
open c;
fetch c into v_emp;
dbms_output.put_line(v_emp.ename);
close c;
end;
---游标，循环取出所有的记录。
declare
cursor c is
select * from emp;
v_emp c%rowtype;
begin
open c;
loop
fetch c into v_emp;
exit when (c%notfound);
dbms_output.put_line(v_emp.ename);
end loop;
close c;
end;
---游标while 循环
declare
cursor c is
select * from emp;
v_emp c%rowtype;
begin
open c;
fetch c into v_emp;
while (c%found) loop
dbms_output.put_line(v_emp.ename);
fetch c into v_emp;
end loop;
close c;
end;
---for循环 不用声明变量，不用open游标 不用close游标 不用fetch
declare
cursor c is
select * from emp;
begin
for v_emp in c loop
dbms_output.put_line(v_emp.ename);
end loop;
end;
---带参数的游标
declare
cursor c(v_deptno emp.deptno%type, v_job emp.job%type)
is
select ename,sal from emp where deptno = v_deptno and job = v_job;
begin
for v_temp in c(30,'CLERK') loop
dbms_output.put_line(v_temp.ename);
end loop;
end;
---课更新的游标
declare
cursor c
is
select * from emp2 for update;
begin
for v_temp in c loop
if (v_temp.sal < 2000) then
update emp2 set sal = sal * 2 where current of c;
elsif (v_temp.sal = 5000) then
delete from emp2 where current of c;
end if;
end loop;
commit;
end;
----创建存储过程
create or replace procedure p
is
cursor c is
select * from emp2 for update;
begin
for v_emp in c loop
if (v_emp.deptno = 10) then
update emp2 set sal = sal + 10 where current of c;
elsif (v_emp.deptno = 20) then
update emp2 set sal = sal + 20 where current of c;
else
update emp2 set sal = sal + 50 where current of c;
end if;
end loop;
commit;
end;
---执行存储过程
exec p;
---或者
begin
p;
end;
---带参数的存储过程
create or replace procedure
max_num(v_a in number,v_b number,v_ret out number,v_temp in out number)
is
begin
if(v_a > v_b) then
v_ret := v_a;
else
v_ret := v_b;
end if;
v_temp := v_temp + 1;
end;
---调用这个存储过程
declare
v_a number :=3;
v_b number :=4;
v_ret number;
v_temp number :=5;
begin
max_num(v_a, v_b, v_ret, v_temp);
dbms_output.put_line(v_ret);
dbms_output.put_line(v_temp);
end;
---函数
create or replace function
sal_tax(v_sal number)
return number
is
begin
if (v_sal < 2000) then
return 0.10;
elsif (v_sal < 2750) then
return 0.15;
else
return 0.20;
end if;
end;
--调用这个函数(别的函数怎么用，这个函数就怎么用)
select ename,sal,sal_tax(sal) from emp;
----触发器
--创建一个日志表
create table emp2_log
(
uname varchar2(20),
action varchar2(10),
atime date
);
--创建一个触发器
create or replace trigger trig
after insert or delete or update on emp2 for each row
begin
if inserting then
insert into emp2_log values (user,'insert',sysdate);
elsif updating then
insert into emp2_log values (user,'update',sysdate);
elsif deleting then
insert into emp2_log values (user,'delete',sysdate);
end if;
end;
--调用这个触发器
update emp2 set sal = sal*2 where deptno = 30;
---更改有依赖关系的表的字段值的建立的一个触发器
create or replace trigger trip_change
after update on dept2
for each row
begin
update emp2 set deptno = :NEW.deptno where deptno = :OLD.deptno;
end;
---触发这个触发器
update dept2 set deptno = 99 where deptno = 10;
---树状结构的存储与展示
drop table article;
create table article
(
id number primary key,
cont varchar2(4000),
pid number,
isleaf number(1),--0 代表非叶子节点，1 代表叶子节点
alevel number(2)
);
insert into article values(1,'蚂蚁大战大象',0,0,0);
insert into article values(2,'蚂蚁大战大象',1,0,1);
insert into article values(3,'蚂蚁大战大象',2,1,2);
insert into article values(4,'蚂蚁大战大象',2,0,2);
insert into article values(5,'蚂蚁大战大象',4,1,3);
insert into article values(6,'蚂蚁大战大象',1,0,1);
insert into article values(7,'蚂蚁大战大象',6,1,2);
insert into article values(8,'蚂蚁大战大象',6,1,2);
insert into article values(9,'蚂蚁大战大象',2,0,2);
insert into article values(10,'蚂蚁大战大象',9,1,3);
commit;
---用存储过程展示树状结构(用递归的方式实现)
create or replace procedure p_tree(v_pid article.pid%type, v_level binary_integer) is
cursor c is select * from article where pid = v_pid;
v_preStr varchar2(1024) :='';
begin
for i in 1..v_level loop
v_preStr := v_preStr || '****';
end loop;
for v_article in c loop
dbms_output.put_line(v_preStr || v_article.cont);
if(v_article.isleaf = 0) then
p_tree(v_article.id, v_level + 1);
end if;
end loop;
end;
--执行这个存储过程
exec p_tree(0,0);
--SQL> exec p_tree(0,0);
--蚂蚁大战大象
--****蚂蚁大战大象
--********蚂蚁大战大象
--********蚂蚁大战大象
--************蚂蚁大战大象
--********蚂蚁大战大象
--************蚂蚁大战大象
--****蚂蚁大战大象
--********蚂蚁大战大象
--********蚂蚁大战大象
--PL/SQL 过程已成功完成。
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