经典sql语句

本文章将详细介绍oracle数据操作中的一些详细的sql

基本sql字符函数数学函数日期时间处理函数聚合函数

---

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;