欢迎您访问程序员文章站本站旨在为大家提供分享程序员计算机编程知识!
您现在的位置是: 首页  >  IT编程

Oracle中常用SQL语句(一)

程序员文章站 2023-03-27 22:32:04
Oracle中常用SQL语句(一) 1、常用SQL --新建表: create table table1( id varchar(300) primary key, name...

Oracle中常用SQL语句(一)

1、常用SQL

--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;

2、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(-1,3,5,7,9) 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; --如果sccore为空,则为10,否则为score

3、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1

4、分页查询(假设每页显示10条)

4.1 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;

4.2 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;