常用sql语句及案例

Posted 2020-10-19 未风

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);