Oracle的自动增量

Question

我需要创建一个序列和一个触发器来自动增加表上的主键,但我不知道如何做到这一点.

Answer 1

创建表和序列

SQL> create table staff (
  2    emp_id number primary key,
  3    staff_name varchar2(100)
  4  );

Table created.

SQL> create sequence emp_id_seq;

Sequence created.

现在,您可以创建一个使用序列填充主键的触发器

SQL> create trigger trg_emp_id
  2    before insert on staff
  3    for each row
  4  begin
  5    select emp_id_seq.nextval
  6      into :new.emp_id
  7      from dual;
  8  end;
  9  /

Trigger created.

现在,当您插入数据时,您无需指定EMP_ID列 - 它将自动由触发器填充

SQL> insert into staff( staff_name ) values ('Justin');

1 row created.

SQL> select * from staff;

    EMP_ID STAFF_NAME
---------- --------------------
         1 Justin

Answer 2

阅读这篇美丽的文章.

序列如何[在oracle中自动增量]

句法

Create sequence sequence_name
start with value
increment by value
minvalue value
maxvalue value;

例

SQL> create table emp (
emp_id number(10),
fname varchar2(25),
lname varchar2(25),
constraint pk_emp_id PRIMARY KEY(emp_id)
);

SQL> Create sequence emp_sequence
start with 1
increment by 1
minvalue 1
maxvalue 10000;

SQL> insert into emp (emp_id,fname,lname) values(emp_sequence.nextval,'Darvin','Johnson');
SQL> insert into emp (emp_id,fname,lname) values(emp_sequence.nextval,'Mig','Andrews');
SQL> insert into emp (emp_id,fname,lname) values(emp_sequence.nextval,'Alex','Martin');
SQL> insert into emp (emp_id,fname,lname) values(emp_sequence.nextval,'Jon','paul');
SQL> insert into emp (emp_id,fname,lname) values(emp_sequence.nextval,'Yatin','Bones');

在emp_sequence.nextval哪里emp_sequence是我们在上面创建的序列的名称,并且nextval是一个用于next number from emp_sequence to emp_id在emp表中分配列的函数.

SQL> select * from emp;

  EMP_ID FNAME                     LNAME
---------- ------------------------- -------------------------
         1 Darvin                    Johnson
         2 Mig                       Andrews
         3 Alex                      Martin
         4 Jon                       paul
         5 Yatin                     Bones

Answer 3

试试这个:

create sequence seq_EmpID start with 1 increment by 1

 insert into Emp_Table values(seq_EmpID.nextval,'Ram')