oracel数据库之SQL

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,

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;

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') 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

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

student表如下：

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;

语句1结果：11

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;

语句3输出结果：

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

--stddev

select stddev(score) from student;

select classno, stddev(score) score from student group by classno;

sum

--sum

select sum(score) from student;

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

median--中位数

--median

select median(score) from student;

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

案例1--学生选课

1. 创建表 stu（学生表），course（课程表），选课表（s_c）

--创建表

create table STU

(

id NUMBER not null,

name VARCHAR2(255)

) ;

create table COURSE

(

id NUMBER not null,

coursename VARCHAR2(255)

) ;

create table S_C

(

sid NUMBER,

cid NUMBER,

score NUMBER

);

2.插入数据

--插入数据

Insert into STU (ID,NAME) values (1,'wish');

Insert into STU (ID,NAME) values (2,'rain');

Insert into STU (ID,NAME) values (3,'july');

Insert into STU (ID,NAME) values (4,'joey');

Insert into COURSE (ID,COURSENAME) values (1,'math');

Insert into COURSE (ID,COURSENAME) values (2,'english');

Insert into COURSE (ID,COURSENAME) values (3,'Japanese');

Insert into COURSE (ID,COURSENAME) values (4,'chinese');

Insert into S_C (SID,CID,SCORE) values (1,1,80);

Insert into S_C (SID,CID,SCORE) values (1,2,90);

Insert into S_C (SID,CID,SCORE) values (2,4,100);

Insert into S_C (SID,CID,SCORE) values (4,4,90);

Insert into S_C (SID,CID,SCORE) values (4,1,100);

Insert into S_C (SID,CID,SCORE) values (4,3,80);

Insert into S_C (SID,CID,SCORE) values (4,2,80);

Insert into S_C (SID,CID,SCORE) values (2,1,90);

Insert into S_C (SID,CID,SCORE) values (2,4,100);

Insert into S_C (SID,CID,SCORE) values (3,1,60);

3.查询学生选课情况

with vt as

(select s.id,s.name,c.coursename,sc.score from stu s, course c, s_c sc where s.id=sc.sid and c.id=sc.cid)

select * from vt order by id;

结果：

案例2--图书馆借阅

1.创建表：图书（book），读者（reader），借阅（borrow）

--创建表 book

create table book(

bookId varchar2(30), --图书总编号

sortid varchar2(30), --分类号

bookname varchar2(100), --书名

author varchar2(30), --作者

publisher varchar2(100),--出版单位

price number(6,2) --价格

);

--创建表 reader

create table reader (

cardId varchar2(30), --借书证号

org varchar2(100), --单位

name varchar2(100), --姓名

gender varchar2(2), --性别

title varchar2(30), --职称

address varchar2(100) --地址

);

--创建表 borrow

create table borrow(

cardId varchar2(30), --借书证号

bookId varchar2(30), --图书总编号

borrowDate varchar2(30) --借阅时间

);

2.插入数据

--插入数据-book

insert into book (bookId,sortid,bookname,author,publisher,price)

values ('aaa','a1','gone with the wind','CA','renmin','103');

insert into book (bookId,sortid,bookname,author,publisher,price)

values ('bbb','a2','the little prince','CB','jixie','30');

insert into book (bookId,sortid,bookname,author,publisher,price)

values ('ccc','a3','the ordinary world','CC','renmin','130');

insert into book (bookId,sortid,bookname,author,publisher,price)

values ('ddd','a4','the little women','CA','dianzi','110');

--插入数据-reader