Oracle数据库常用语法

Oracle数据库常用语法

Scroll Down

公司需要使用Oracle,在这里记录一下基本使用SQL语法.
原文章:https://blog.csdn.net/lslby123/article/details/79863539

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 

数字函数

--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


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; 

查询子集

-- 创建表
create table employee(
       emp_id number(18),
       lead_id number(18),
       emp_name varchar2(200),
       salary number(10,2),
       dept_no varchar2(8)
);

-- 添加数据
insert into employee values('1',0,'king','1000000.00','001');
insert into employee values('2',1,'jack','50500.00','002');
insert into employee values('3',1,'arise','60000.00','003');
insert into employee values('4',2,'scott','30000.00','002');
insert into employee values('5',2,'tiger','25000.00','002');
insert into employee values('6',3,'wudde','23000.00','003');
insert into employee values('7',3,'joker','21000.00','003');commit;

    select emp_id,lead_id,emp_name,salary
       from employee 
       start with emp_id=6
       connect by prior lead_id=emp_id;

811555201905241003435931838453429.png