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

常用sql语句及案例
--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  when 1 then ‘女’ end  ) gender from  table1 
 

常用sql语句及案例

 

数学函数

常用sql语句及案例
--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;
常用sql语句及案例

 

 

 

 rownum相关

常用sql语句及案例
--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
常用sql语句及案例

 

 分页查询

(假设每页显示10条)

不包含排序:

常用sql语句及案例
--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;
常用sql语句及案例

包含排序:

常用sql语句及案例
--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;
常用sql语句及案例

 

 时间处理

1. to_char和to_date基本使用

常用sql语句及案例
--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
常用sql语句及案例

eg1:

常用sql语句及案例
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;
常用sql语句及案例

常用sql语句及案例

eg2:

常用sql语句及案例
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;
常用sql语句及案例

常用sql语句及案例

 

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;   

常用sql语句及案例

 

3)next_day

select sysdate today, next_day(sysdate,6) nextweek from dual;

常用sql语句及案例

 

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

常用sql语句及案例
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; 
常用sql语句及案例

 

常用sql语句及案例

 

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; 

常用sql语句及案例

 

 

字符函数

常用sql语句及案例
--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;
常用sql语句及案例

 

常用sql语句及案例

 

 

to_number

常用sql语句及案例
--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;
常用sql语句及案例

常用sql语句及案例

 

 

聚合函数

student表如下:

常用sql语句及案例

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:

常用sql语句及案例

 

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)

常用sql语句及案例
--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  
);
常用sql语句及案例

 

2.插入数据

常用sql语句及案例
--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);
常用sql语句及案例

 

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:

常用sql语句及案例

 

 

案例2--图书馆借阅

1.创建表: 图书(book),读者(reader),借阅(borrow)

常用sql语句及案例
--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
);
常用sql语句及案例

 

2.插入数据

常用sql语句及案例
--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);
常用sql语句及案例

表信息如下:

book------> reader-------> borrow

常用sql语句及案例

常用sql语句及案例

常用sql语句及案例

 

 

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);

常用sql语句及案例

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);

常用sql语句及案例

 

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;

常用sql语句及案例

 

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  when gender=2 then  else 其他 end gender
from reader where name like m%;

常用sql语句及案例

 

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); 

 

常用sql语句及案例

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); 

常用sql语句及案例

 

3)查询+去重+读者姓名等信息

常用sql语句及案例
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);
常用sql语句及案例

常用sql语句及案例

 

 

 

 

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常用sql语句及案例

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