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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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