经典SQL语句

/***基础sql/ 以下主要列出来常用的sql

--新建表： create table table_name( id varchar2(300) primary key, name varchar2(200) not null );

--插入数据
insert into table_name (id,name) values ('aa','bb');

--更新数据
update table_name set id = 'bb' where id='cc';

--删除数据
delete from table_name where id ='cc';

--删除表
drop table table_name;

--修改表名： alter table table_name rename to table_name_1;

--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

字符函数 --字符函数 select substr('abcdefg',1,5)substr, --字符串截取 instr('abcdefg','bc') instr, --查找子串

   'Hello'||'World' concat,                         --连接

   trim('  wish  ') trim,                           --去前后空格
   rtrim('wish  ') rtrim,                           --去后面空格
   ltrim('  wish') ltrim,                           --去前面空格

   trim(leading 'w' from 'wish') deleteprefix,      --去前缀
   trim(trailing 'h' from 'wish') deletetrailing,   --去后缀
   trim('w' from 'wish') trim1,

   ascii('A') A1, 
   ascii('a') A2,                                   --ascii(转换为对应的十进制数)
   chr(65) C1, 
   chr(97) C2,                                      --chr(十进制转对应字符)

   length('abcdefg') len,                           --length 

   lower('WISH')lower, 
   upper('wish')upper, 
   initcap('wish')initcap,                            --大小写变换

   replace('wish1','1','youhappy') replace,           --替换

   translate('wish1','1','y')translate,               --转换，对应一位(前面的位数大于等于后面的位数)
   translate('wish1','sh1','hy')translate1,

   concat('11','22') concat          　　　　　　　　   --连接

from dual;

--to_number

--to_number(expr) --to_number(expr,format) --to_number(expr,format,'nls-param')

select to_number('0123')number1, --converts a string to number trunc(to_number('0123.123'),2) number2, to_number('120.11','999.99') number3, 　　　 to_number('0a','xx') number4, --converts a hex number to decimal to_number(100000,'xxxxxx') number5

from dual;

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;

日期函数 --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

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

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

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

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

--时间区间 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');

--interval 间隔 select to_char(sysdate,'yyyy-mm-dd hh24:mi:ss') currenttime, to_char(sysdate - interval '7' year,'yyyy-mm-dd hh24:mi:ss') intervalyear,
to_char(sysdate - interval '7' month,'yyyy-mm-dd hh24:mi:ss') intervalMonth,
to_char(sysdate - interval '7' day,'yyyy-mm-dd hh24:mi:ss') intervalday,
to_char(sysdate - interval '7' hour,'yyyy-mm-dd hh24:mi:ss') intervalHour,
to_char(sysdate - interval '7' minute,'yyyy-mm-dd hh24:mi:ss') intervalMinute,
to_char(sysdate - interval '7' second,'yyyy-mm-dd hh24:mi:ss') intervalSecond
from dual;

--add_months 增加月份 select add_months(sysdate,12) newtime from dual;

--extract select extract(month from sysdate) "This Month", extract(year from add_months(sysdate,36)) " Years" from dual;

聚合函数 --count select count(1) as count from student;--效率最高 select count(*) as count from student;
select count(distinct score) from student;

--avg --distinct|all select avg(score) score from student; select avg(distinct score) from student; select classno,avg(score) score from student group by classno;

--max --distinct|all select max(score) from student; select classno, max(score) score from student group by classno;

--min --distinct|all select min(score) from student; select classno, min(score) score from student group by classno;

--stddev（standard deviation）标准差 select stddev(score) from student; select classno, stddev(score) score from student group by classno;

--sum select sum(score) from student; select classno, sum(score) score from student group by classno;

--median--中位数 select median(score) from student; select classno, median(score) score from student group by classno;

伪列rownum --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 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 where rownum<9 where p.rn>6;--效率远高于方式一

分页查询 --假设每页显示10条

--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;

--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 ( )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 where rownum<=20 )p where p.rn>=10;