ORACLE sequence

Statement to create sequence (example)

create sequence seq_course
minvalue 1
maxvalue 999999999999999999
start with 1
increment by 2
cache 20;

Query the size of the next value of a sequence using a sequence in conjunction with a table

SELECT seq_course.nextval FROM dual;

--Using sequences to realize the self-increment operation of the primary key

INSERT INTO TEST values(seq_course.nextval ,'aa','cc','ss');

transaction commit

INSERT INTO TEST values(seq_course.nextval ,'fsfv','asdqw','qdc');
COMMIT;

transaction rollback

rollback has the opportunity to roll back the savepoint savepoint of the transaction transaction before committing

--savepoint 保存点
INSERT INTO TEST values(seq_course.nextval ,'fsfv12','asdqw','qdc');
INSERT INTO TEST values(seq_course.nextval ,'fsfv13','asdqw','qdc');
SAVEPOINT a1; --Create a transaction savepoint 
INSERT  INTO TEST values ​​(seq_course.nextval , ' fsfv14 ' , ' asdqw ' , ' qdc ' );
 --Rollback to transaction savepoint a1 
ROLLBACK  TO a1;
 --Commit operation 
COMMIT ;

view

create or replace view emp_dept as
  select e.ename,e.job,d.dname
    from emp e,dept d
   where e.deptno=d.deptno

In the above example, authorization can be made in the syatem account and authorized to scott

--authorize grant 
create view to scott _   

Function: Views store complex query operations, and users (developers) can easily query the views to get the desired data

When querying data later, it is more convenient to write directly and query directly:

select * from emp_dept;