oracle基础知识

-- 表
create table test (names varchar2(12),
dates date,
num int,
dou double);
-- 视图
create or replace view vi_test as
select * from test;

-- 同义词
create or replace synonym aa
for dbusrcard001.aa;

-- 存储过程
create or replace produce dd(v_id in employee.empoy_id%type)
as
begin

end
dd;

-- 函数
create or replace function ee(v_id in employee%rowtype) return varchar(15)
is
var_test varchar2(15);
begin
return var_test;
exception when others then

end

-- 三种触发器的定义
create or replace trigger ff
alter delete
on test
for each row
declare
begin
delete from test;
if sql%rowcount < 0 or sql%rowcount is null then
rais_replaction_err(-20004,"错误")
end if
end

create or replace trigger gg
alter insert
on test
for each row
declare
begin
if :old.names = :new.names then
raise_replaction_err(-2003,"编码重复");
end if
end

create or replace trigger hh
for update
on test
for each row
declare
begin
if updating then
if :old.names <> :new.names then
reaise_replaction_err(-2002,"关键字不能修改")
end if
end if
end

-- 定义游标
declare
cursor aa is
select names,num from test;
begin
for bb in aa
loop
if bb.names = "ORACLE" then

end if
end loop;

end

-- 速度优化，前一语句不后一语句的速度快几十倍
select names,dates
from test,b
where test.names = b.names(+) and
b.names is null and
b.dates > date('2003-01-01','yyyy-mm-dd')

select names,dates
from test
where names not in ( select names
from b
where dates > to_date('2003-01-01','yyyy-mm-dd'))

-- 查找重复记录
select names,num
from test
where rowid != (select max(rowid)
from test b
where b.names = test.names and
b.num = test.num)

-- 查找表TEST中时间最新的前10条记录
select * from (select * from test order by dates desc) where rownum < 11

-- 序列号的产生
create sequence row_id
minvalue 1
maxvalue 8888888888888888888888
start with 1
increment by 1

insert into test values(row_id.nextval,....)

create table EMP
(
EMPNO NUMBER(4) not null,
ENAME VARCHAR2(10),
JOB VARCHAR2(9),
MGR NUMBER(4),
HIREDATE DATE,
SAL NUMBER(7,2),
COMM NUMBER(7,2),
DEPTNO NUMBER(2)
)
tablespace USERS
pctfree 10
initrans 1
maxtrans 255
storage
(
initial 64K
minextents 1
maxextents unlimited
);
comment on column EMP.EMPNO
is '雇员编号';
comment on column EMP.ENAME
is '雇员的名称';
comment on column EMP.JOB
is '职位';
comment on column EMP.MGR
is '该员工的上级的编号';
comment on column EMP.HIREDATE
is '入职日期';
comment on column EMP.SAL
is '薪水';
comment on column EMP.COMM
is '奖金';
comment on column EMP.DEPTNO
is '部门编号';
alter table EMP
add constraint PK_EMP primary key (EMPNO)
using index
tablespace USERS
pctfree 10
initrans 2
maxtrans 255
storage
(
initial 64K
minextents 1
maxextents unlimited
);
alter table EMP
add constraint FK_DEPTNO foreign key (DEPTNO)
references DEPT (DEPTNO);

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oracle--sign

取数字n的符号,大于0返回1,小于0返回-1,等于0返回0

SQL> select sign(100),sign(-100),sign(0) from dual;

SIGN(123) SIGN(-100) SIGN(0)

--------- ---------- ---------

1 -1 0

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decode 用法：