数据库Oracle基本命令
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
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
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
insert into reader(cardid, org, name,gender, title, address)
values ('xxx','A','wish','1','student','bupt');
insert into reader(cardid, org, name,gender, title, address)
values ('uuu','A','luna','1','student','bupt');
insert into reader(cardid, org, name,gender, title, address)
values ('vvv','B','harry','1','student','bupt');
insert into reader(cardid, org, name,gender, title, address)
values ('www','C','chander','2','professor','bupt');
insert into reader(cardid, org, name,gender, title, address)
values ('yyy','A','joey','2','student','bupt');
insert into reader(cardid, org, name,gender, title, address)
values ('zzz','B','richard','2','student','bupt');
insert into reader(cardid, org, name,gender, title, address)
values ('OOO','A','micheal','2','student','bupt');
insert into reader(cardid, org, name,gender, title, address)
values ('ppp','A','richal','2','student','bupt');
insert into reader(cardid, org, name,gender, title, address)
values ('abp','A','michal','2','student','bupt');
insert into reader(cardid, org, name,gender, title, address)
values ('ccp','A','mike','2','student','bupt');
--插入数据-borrow
insert into borrow(cardid,bookid,borrowdate) values('xxx','aaa','2014-4-29');
insert into borrow(cardid,bookid,borrowdate) values('xxx','bbb','2014-4-29');
insert into borrow(cardid,bookid,borrowdate) values('xxx','ccc','2014-4-28');
insert into borrow(cardid,bookid,borrowdate) values('yyy','ccc','2014-4-28');
insert into borrow(cardid,bookid,borrowdate) values('yyy','ddd','2014-4-27');
insert into borrow(cardid,bookid,borrowdate) values('yyy','aaa','2014-4-27');
insert into borrow(cardid,bookid,borrowdate) values('zzz','bbb','2014-4-28');
insert into borrow(cardid,bookid,borrowdate) values('zzz','ddd','2014-4-27');
insert into borrow(cardid,bookid,borrowdate) values('zzz','aaa','2014-4-27');
insert into borrow(cardid,bookid,borrowdate) values('uuu','bbb','2014-4-28');
insert into borrow(cardid,bookid,borrowdate) values('uuu','ddd','2014-4-27');
insert into borrow(cardid,bookid,borrowdate) values('uuu','aaa','2014-4-27');
insert into borrow(cardid,bookid,borrowdate) values('uuu','ccc','2014-4-26');
insert into borrow(cardid,bookid,borrowdate) values('vvv','bbb','2014-4-28');
insert into borrow(cardid,bookid,borrowdate) values('vvv','ddd','2014-4-27');
insert into borrow(cardid,bookid,borrowdate) values('www','aaa','2014-4-27');
insert into borrow(cardid,bookid,borrowdate) values('www','ccc','2014-4-26');
表信息如下：
book------> reader-------> borrow
3. 查询A单位借阅图书的读者人数和人员详细信息
人数：
with vt1 as
(select cardid from reader where reader.org='A')
select count(1) from vt1 where exists (select cardid from borrow where borrow.cardid=vt1.cardid);
详细信息：
with vt1 as
(select cardid,name,org from reader where reader.org='A')
select cardid,name,org from vt1 where exists (select cardid from borrow where borrow.cardid=vt1.cardid);
4.查询借书证号尾字符为'p'的读者
select cardid, name, org from reader where cardid like '%p';
5. 查询名字以m开头的女性读者，‘1’显示为女，‘2’显示为男
select cardid, name, org,
case when gender='1' then '女' when gender='2' then '男' else '其他' end gender
from reader where name like 'm%';
6. 2014年2-4月借过书的读者
1)查询满足条件的读者（仅包含cardid）--未去重
方式一：
select cardid, borrowdate from borrow where to_char(to_date(borrowdate,'yyyy-mm-dd'),'yyyy')='2014'
and to_char(to_date(borrowdate,'yyyy-mm-dd'),'mm')>='02'
and to_char(to_date(borrowdate,'yyyy-mm-dd'),'mm')<='04';
方式二：
select cardid, borrowdate from borrow where to_char(to_date(borrowdate,'yyyy-mm-dd'),'yyyy')='2014' --查询
and to_char(to_date(borrowdate,'yyyy-mm-dd'),'yyyy-mm')>='2014-02'
and to_char(to_date(borrowdate,'yyyy-mm-dd'),'yyyy-mm')<='2014-04';
方式三：
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');
2) 查询+去重
select distinct cardid from borrow where to_char(to_date(borrowdate,'yyyy-mm-dd'),'yyyy')='2014' --查询+去重
and to_char(to_date(borrowdate,'yyyy-mm-dd'),'yyyy-mm')>='2014-02'
and to_char(to_date(borrowdate,'yyyy-mm-dd'),'yyyy-mm')<='2014-04';
select distinct cardid 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');
3）查询+去重+读者姓名等信息
with vt1 as
(select distinct cardid from borrow where to_char(to_date(borrowdate,'yyyy-mm-dd'),'yyyy')='2014'
and to_char(to_date(borrowdate,'yyyy-mm-dd'),'yyyy-mm')>='2014-02'
and to_char(to_date(borrowdate,'yyyy-mm-dd'),'yyyy-mm')<='2014-04')
select cardid, name,org from reader where exists (select cardid from vt1 where vt1.cardid=reader.cardid);
ALTER TABLE：添加，修改，删除表的列，约束等表的定义。
查看列：desc 表名;
修改表名：alter table t_book rename to bbb;
添加列：alter table 表名 add column 列名 varchar(30);
删除列：alter table 表名 drop column 列名;
修改列名MySQL： alter table bbb change nnnnn hh int;
修改列名SQLServer：exec sp_rename't_student.name','nn','column';
修改列名Oracle：lter table bbb rename column nnnnn to hh int;
修改列属性：alter table t_book modify name varchar(22);
sp_rename：SQLServer 内置的存储过程，用与修改表的定义。
MySQL 查看约束，添加约束，删除约束 添加列，修改列，删除列
查看表的字段信息：desc 表名;
查看表的所有信息：show create table 表名;
添加主键约束：alter table 表名 add constraint 主键 (形如：PK_表名) primary key 表名(主键字段);
添加外键约束：alter table 从表 add constraint 外键(形如：FK_从表_主表) foreign key 从表(外键字段) references 主表(主键字段);
删除主键约束：alter table 表名 drop primary key;
删除外键约束：alter table 表名 drop foreign key 外键(区分大小写);
修改表名：alter table t_book rename to bbb;
添加列：alter table 表名 add column 列名 varchar(30);
删除列：alter table 表名 drop column 列名;
修改列名MySQL： alter table bbb change nnnnn hh int;
修改列名SQLServer：exec sp_rename't_student.name','nn','column';
修改列名Oracle：alter table bbb rename column nnnnn to hh int;
修改列属性：alter table t_book modify name varchar(22);
sp_rename：SQLServer 内置的存储过程，用与修改表的定义。
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