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Oracle数据库常用语法

发布时间:2020-12-25 20:55:14 所属栏目:站长百科 来源:网络整理
导读:基本 --新建表: create table table1( id varchar(300) primary key,name varchar(200) not null); --插入数据 insert into table1 (id,name) values (‘aa‘,‘bb‘); --更新数据 update table1 set id = ‘bb‘ where id=‘cc‘; --删除数据 delete from
副标题[/!--empirenews.page--]

基本
--新建表:
create table table1( id varchar(300) primary key,name varchar(200) not null);

--插入数据
insert into table1 (id,name) values (‘aa‘,‘bb‘);

--更新数据
update table1 set id = ‘bb‘ where id=‘cc‘;

--删除数据
delete from table1 where id =‘cc‘;

--删除表
drop table table1;

--修改表名:
alter table table1 rename to table2;

--表数据复制:
insert into table1 (select * from table2);

--复制表结构:
create table table1 select * from table2 where 1>1;

--复制表结构和数据:
create table table1 select * from table2;

--复制指定字段:
create table table1 as select id,name from table2 where 1>1;

--条件查询:
select id,name (case gender when 0 then ‘男‘ when 1 then ‘女’ end ) gender from table1
数学函数
--绝对值:abs()
select abs(-2) value from dual; --(2)

--取整函数(大):ceil()
select ceil(-2.001) value from dual; --(-2)

--取整函数(小):floor()
select floor(-2.001) value from dual; --(-3)

--取整函数(截取):trunc()
select trunc(-2.001) value from dual; -- (-2)

--四舍五入:round()
select round(1.234564,4) value from dual; --(1.2346)

--取平方:Power(m,n)
select power(4,2) value from dual; --(16)

--取平方根:SQRT()
select sqrt(16) value from dual; --(4)

--取随机数:dbms_random(minvalue,maxvalue)
select dbms_random.value() from dual; (默认是0到1之间)
 select dbms_random.value(2,4) value from dual; (2-4之间随机数)

--取符号:Sign()
  select sign(-3) value from dual; --(-1)
  select sign(3) value from dual; --(1)


--取集合的最大值:greatest(value)
select greatest(-1,3,5,7,9) value from dual; --(9)

--取集合的最小值:least(value)
select least(-1,9) value from dual; --(-1)

--处理Null值:nvl(空值,代替值)
select nvl(null,10) value from dual; --(10)
  
select nvl(score,10) score from student;
rownum相关
--rownum小于某个数时可以直接作为查询条件(注意oracle不支持select top)
select * from student where rownum <3;

--查询rownum大于某个数值,需要使用子查询,并且rownum需要有别名
select * from(select rownum rn,id,name from student) where rn>2;
select * from (select rownum rn,student.* from student) where rn >3;

--区间查询
select * from (select rownum rn,student.* from student) where rn >3 and rn<6;

--排序+前n条
select * from (select rownum rn,t.* from ( select d.* from DJDRUVER d order by drivernumber)t )p where p.rn<10;

--排序+区间查询1
select * from (select rownum rn,t.* from ( select d.* from DJDRIVER d order by DJDRIVER_DRIVERTIMES)t )p where p.rn<9 and p.rn>6;

--排序+区间查询2
select * from (select rownum rn,t.* from ( select d.* from DJDRIVER d order by DJDRIVER_DRIVERTIMES)t where rownum<9 )p where p.rn>6;--效率远高于方式一
?分页查询
(假设每页显示10条)

不包含排序:

--效率低

select * from (select rownum rn,d.* from DJDRIVER d )p where p.rn<=20 and p.rn>=10;

select * from (select rownum rn,d.* from DJDRIVER d )p where p.rn between 10 and 20;

--效率高

select * from (select rownum rn,d.* from DJDRIVER d where rownum<=20 )p where p.rn>=10;
包含排序:
--排序+区间查询1(效率低)

select * from (select rownum rn,t.* from ( select d.* from DJDRIVER d order by DJDRIVER_DRIVERTIMES)t )p where p.rn<=20 and p.rn>=10;

select * from (select rownum rn,t.* from ( select d.* from DJDRIVER d order by DJDRIVER_DRIVERTIMES)t )p where p.rn between 10 and 20;

--排序+区间查询2(效率高)

select * from (select rownum rn,t.* from ( select d.* from DJDRIVER d order by DJDRIVER_DRIVERTIMES)t where rownum<=20 )p where p.rn>=10;
?时间处理
1. to_char和to_date基本使用

--日期
--年 yyyy yyy yy year
--月 month mm mon month
--日+星期 dd ddd(一年中第几天) dy day
--小时 hh hh24
--分 mi
--秒 ss

eg1:
select to_char(sysdate,‘yyyy-mm-dd hh24:mi:ss‘)currenttime,
to_char(sysdate,‘yyyy‘) year,‘mm‘) month,‘dd‘) day,‘day‘) week,‘hh24‘)hour,‘mi‘) minute,‘ss‘) second
from dual;


eg2:

select to_date(‘2009-07-04 05:02:01‘,
to_char(to_date(‘2009-07-04 05:02:01‘,‘yyyy-mm-dd hh24:mi:ss‘),‘yyyy‘)year,‘mm‘)month,‘day‘,‘NLS_DATE_LANGUAGE=American‘) week,--设置语言
to_char(to_date(‘2009-07-04 05:02:01‘,‘ss‘) second
from dual;


2)months_between

select months_between(to_date(‘03-31-2014‘,‘MM-DD-YYYY‘),to_date(‘12-31-2013‘,‘MM-DD-YYYY‘)) "MONTHS"
FROM DUAL;


3)next_day

select sysdate today,next_day(sysdate,6) nextweek from dual;


4)时间区间

例:

select cardid,borrowdate from borrow where to_date(borrowdate,‘yyyy-mm-dd hh24:mi:ss‘) between
to_date(‘2014-02-01 00:00:00‘,‘yyyy-mm-dd hh24:mi:ss‘) and
to_date(‘2014-05-01 00:00:00‘,‘yyyy-mm-dd hh24:mi:ss‘);

5)interval

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