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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(-1,3,5,7,9) 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;
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1select * 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2select * 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, 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') secondfrom dual;
eg2:
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') secondfrom 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
eg：
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
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;
6）add_months
select add_months(sysdate,12) newtime from dual;
7)extract
select extract(month from sysdate) "This Month", extract(year from add_months(sysdate,36)) " Years" from dual;
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;聚合函数
count：
--count (distinct|all)select count(1) as count from student;--效率最高select count(*) as count from student; select count(distinct score) from student;
avg
--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
--max (distinct|all)select max(score) from student;select classno, max(score) score from student group by classno;
min
--min (distinct|all)select min(score) from student;select classno, min(score) score from student group by classno;
stddev（standard deviation）标准差
--stddevselect stddev(score) from student;select classno, stddev(score) score from student group by classno;
sum
--sumselect sum(score) from student;select classno, sum(score) score from student group by classno;
median--中位数
--medianselect median(score) from student;select classno, median(score) score from student group by classno;