常用sql语句及案例

目录

1）基本

2）数学函数

3）rownum

4）分页

5）时间处理

6）字符函数

7）to_number

8）聚合函数

9）学生选课

10）图书馆借阅

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;

--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) 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 sys.dbms.random.value(0,1) value from dual;

--取符号：Sign()
   select sign(-3) value from dual;       --(-)

--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
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);