How to create id with AUTO_INCREMENT on Oracle?

It appears that there is no concept of AUTO_INCREMENT in Oracle, up until and including version 11g.

How can I create a column that behaves like auto increment in Oracle 11g?

There is no such thing as "auto_increment" or "identity" columns in Oracle as of Oracle 11g. However, you can model it easily with a sequence and a trigger:

Table definition:

CREATE TABLE departments (
  ID           NUMBER(10)    NOT NULL,
  DESCRIPTION  VARCHAR2(50)  NOT NULL);

ALTER TABLE departments ADD (
  CONSTRAINT dept_pk PRIMARY KEY (ID));

CREATE SEQUENCE dept_seq START WITH 1;

Trigger definition:

CREATE OR REPLACE TRIGGER dept_bir 
BEFORE INSERT ON departments 
FOR EACH ROW

BEGIN
  SELECT dept_seq.NEXTVAL
  INTO   :new.id
  FROM   dual;
END;
/

###UPDATE:

IDENTITY column is now available on Oracle 12c:

create table t1 (
	c1 NUMBER GENERATED by default on null as IDENTITY,
	c2 VARCHAR2(10)
	);

or specify starting and increment values, also preventing any insert into the identity column (GENERATED ALWAYS) (again, Oracle 12c+ only)

create table t1 (
	c1 NUMBER GENERATED ALWAYS as IDENTITY(START with 1 INCREMENT by 1),
	c2 VARCHAR2(10)
	);

Alternatively, Oracle 12 also allows to use a sequence as a default value:

CREATE SEQUENCE dept_seq START WITH 1;

CREATE TABLE departments (
  ID           NUMBER(10)    DEFAULT dept_seq.nextval NOT NULL,
  DESCRIPTION  VARCHAR2(50)  NOT NULL);

ALTER TABLE departments ADD (
  CONSTRAINT dept_pk PRIMARY KEY (ID));

SYS_GUID returns a GUID-- a globally unique ID. A SYS_GUID is a RAW(16). It does not generate an incrementing numeric value.

If you want to create an incrementing numeric key, you'll want to create a sequence.

CREATE SEQUENCE name_of_sequence
  START WITH 1
  INCREMENT BY 1
  CACHE 100;

You would then either use that sequence in your INSERT statement

INSERT INTO name_of_table( primary_key_column, <<other columns>> )
  VALUES( name_of_sequence.nextval, <<other values>> );

Or you can define a trigger that automatically populates the primary key value using the sequence

CREATE OR REPLACE TRIGGER trigger_name
  BEFORE INSERT ON table_name
  FOR EACH ROW
BEGIN
  SELECT name_of_sequence.nextval
    INTO :new.primary_key_column
    FROM dual;
END;

If you are using Oracle 11.1 or later, you can simplify the trigger a bit

CREATE OR REPLACE TRIGGER trigger_name
  BEFORE INSERT ON table_name
  FOR EACH ROW
BEGIN
  :new.primary_key_column := name_of_sequence.nextval;
END;

If you really want to use SYS_GUID

CREATE TABLE table_name (
  primary_key_column raw(16) default sys_guid() primary key,
  <<other columns>>
)

In Oracle 12c onward you could do something like,

CREATE TABLE MAPS
(
  MAP_ID INTEGER GENERATED ALWAYS AS IDENTITY (START WITH 1 INCREMENT BY 1) NOT NULL,
  MAP_NAME VARCHAR(24) NOT NULL,
  UNIQUE (MAP_ID, MAP_NAME)
);

---

And in Oracle (Pre 12c).

-- create table
CREATE TABLE MAPS
(
  MAP_ID INTEGER NOT NULL ,
  MAP_NAME VARCHAR(24) NOT NULL,
  UNIQUE (MAP_ID, MAP_NAME)
);

-- create sequence
CREATE SEQUENCE MAPS_SEQ;

-- create tigger using the sequence
CREATE OR REPLACE TRIGGER MAPS_TRG 
BEFORE INSERT ON MAPS 
FOR EACH ROW
WHEN (new.MAP_ID IS NULL)
BEGIN
  SELECT MAPS_SEQ.NEXTVAL
  INTO   :new.MAP_ID
  FROM   dual;
END;
/

Here are three flavors:

1. numeric. Simple increasing numeric value, e.g. 1,2,3,....
2. GUID. globally univeral identifier, as a RAW datatype.
3. GUID (string). Same as above, but as a string which might be easier to handle in some languages.

x is the identity column. Substitute FOO with your table name in each of the examples.

-- numerical identity, e.g. 1,2,3...
create table FOO (
    x number primary key
);
create sequence  FOO_seq;

create or replace trigger FOO_trg
before insert on FOO
for each row
begin
  select FOO_seq.nextval into :new.x from dual;
end;
/

-- GUID identity, e.g. 7CFF0C304187716EE040488AA1F9749A
-- use the commented out lines if you prefer RAW over VARCHAR2.
create table FOO (
    x varchar(32) primary key        -- string version
    -- x raw(32) primary key         -- raw version
);

create or replace trigger FOO_trg
before insert on FOO
for each row
begin
  select cast(sys_guid() as varchar2(32)) into :new.x from dual;  -- string version
  -- select sys_guid() into :new.x from dual;                     -- raw version
end;
/

update:

Oracle 12c introduces these two variants that don't depend on triggers:

create table mytable(id number default mysequence.nextval);
create table mytable(id number generated as identity);

The first one uses a sequence in the traditional way; the second manages the value internally.

Assuming you mean a column like the SQL Server identity column?

In Oracle, you use a SEQUENCE to achieve the same functionality. I'll see if I can find a good link and post it here.

Update: looks like you found it yourself. Here is the link anyway: http://www.techonthenet.com/oracle/sequences.php

Oracle Database 12c introduced Identity, an auto-incremental (system-generated) column. In the previous database versions (until 11g), you usually implement an Identity by creating a Sequence and a Trigger. From 12c onward, you can create your own Table and define the column that has to be generated as an Identity.

Trigger and Sequence can be used when you want serialized number that anyone can easily read/remember/understand. But if you don't want to manage ID Column (like emp_id) by this way, and value of this column is not much considerable, you can use SYS_GUID() at Table Creation to get Auto Increment like this.

CREATE TABLE <table_name> 
(emp_id RAW(16) DEFAULT SYS_GUID() PRIMARY KEY,
name VARCHAR2(30));

Now your emp_id column will accept "globally unique identifier value". you can insert value in table by ignoring emp_id column like this.

INSERT INTO <table_name> (name) VALUES ('name value');

So, it will insert unique value to your emp_id Column.

Starting with Oracle 12c there is support for Identity columns in one of two ways:

1. Sequence + Table - In this solution you still create a sequence as you normally would, then you use the following DDL:

   CREATE TABLE MyTable (ID NUMBER DEFAULT MyTable_Seq.NEXTVAL, ...)

2. Table Only - In this solution no sequence is explicitly specified. You would use the following DDL:

   CREATE TABLE MyTable (ID NUMBER GENERATED AS IDENTITY, ...)

If you use the first way it is backward compatible with the existing way of doing things. The second is a little more straightforward and is more inline with the rest of the RDMS systems out there.

it is called Identity Columns and it is available only from oracle Oracle 12c

CREATE TABLE identity_test_tab
(
   id            NUMBER GENERATED ALWAYS AS IDENTITY,
   description   VARCHAR2 (30)
);

example of insert into Identity Columns as below

INSERT INTO identity_test_tab (description) VALUES ('Just DESCRIPTION');

> 1 row created.

you can NOT do insert like below

INSERT INTO identity_test_tab (id, description) VALUES (NULL, 'ID=NULL and DESCRIPTION');

> ERROR at line 1: ORA-32795: cannot insert into a generated always > identity column

INSERT INTO identity_test_tab (id, description) VALUES (999, 'ID=999 and DESCRIPTION');

> ERROR at line 1: ORA-32795: cannot insert into a generated always > identity column

useful link

Here is complete solution w.r.t exception/error handling for auto increment, this solution is backward compatible and will work on 11g & 12c, specifically if application is in production.

Please replace 'TABLE_NAME' with your appropriate table name

--checking if table already exisits
BEGIN
    EXECUTE IMMEDIATE 'DROP TABLE TABLE_NAME';
    EXCEPTION WHEN OTHERS THEN NULL;
END;
/

--creating table
CREATE TABLE TABLE_NAME (
       ID NUMBER(10) PRIMARY KEY NOT NULL,
	   .
	   .
	   .
);

--checking if sequence already exists
BEGIN
    EXECUTE IMMEDIATE 'DROP SEQUENCE TABLE_NAME_SEQ';
    EXCEPTION WHEN OTHERS THEN NULL;
END;

--creating sequence
/
CREATE SEQUENCE TABLE_NAME_SEQ START WITH 1 INCREMENT BY 1 MINVALUE 1 NOMAXVALUE NOCYCLE CACHE 2;

--granting rights as per required user group
/
GRANT SELECT, INSERT, UPDATE, DELETE ON TABLE_NAME TO USER_GROUP;

-- creating trigger
/
CREATE OR REPLACE TRIGGER TABLE_NAME_TS BEFORE INSERT OR UPDATE ON TABLE_NAME FOR EACH ROW
BEGIN    
    -- auto increment column
    SELECT TABLE_NAME_SEQ.NextVal INTO :New.ID FROM dual;

	-- You can also put some other required default data as per need of your columns, for example
    SELECT SYS_CONTEXT('USERENV', 'SESSIONID') INTO :New.SessionID FROM dual;
    SELECT SYS_CONTEXT('USERENV','SERVER_HOST') INTO :New.HostName FROM dual;
    SELECT SYS_CONTEXT('USERENV','OS_USER') INTO :New.LoginID FROM dual;    
	.
	.
	.
END;
/

This is how I did this on an existing table and column (named id):

UPDATE table SET id=ROWNUM;
DECLARE
  maxval NUMBER;
BEGIN
  SELECT MAX(id) INTO maxval FROM table;
  EXECUTE IMMEDIATE 'DROP SEQUENCE table_seq';
  EXECUTE IMMEDIATE 'CREATE SEQUENCE table_seq START WITH '|| TO_CHAR(TO_NUMBER(maxval)+1) ||' INCREMENT BY 1 NOMAXVALUE';
END;
CREATE TRIGGER table_trigger
  BEFORE INSERT ON table
  FOR EACH ROW
BEGIN
  :new.id := table_seq.NEXTVAL;
END;

FUNCTION GETUNIQUEID_2 RETURN VARCHAR2
AS
v_curr_id NUMBER;
v_inc NUMBER;
v_next_val NUMBER;
pragma autonomous_transaction;
begin 
CREATE SEQUENCE sequnce
START WITH YYMMDD0000000001
INCREMENT BY 1
NOCACHE
select sequence.nextval into v_curr_id from dual;
if(substr(v_curr_id,0,6)= to_char(sysdate,'yymmdd')) then
v_next_val := to_number(to_char(SYSDATE+1, 'yymmdd') || '0000000000');
v_inc := v_next_val - v_curr_id;
execute immediate ' alter sequence sequence increment by ' || v_inc ;
select sequence.nextval into v_curr_id from dual;
execute immediate ' alter sequence sequence increment by 1';
else
dbms_output.put_line('exception : file not found');
end if;
RETURN 'ID'||v_curr_id;
END;

Query to create auto increment in oracle. In below query incrmnt column value will be auto incremented wheneever a new row is inserted

CREATE TABLE table1(
id RAW(16) NOT NULL ENABLE,
incrmnt NUMBER(10,0) GENERATED ALWAYS AS IDENTITY
MINVALUE 1 MAXVALUE 999999999999999999999999999 INCREMENT BY 1 START WITH 1 NOORDER NOCYCLE NOT NULL ENABLE,
CONSTRAINT PK_table1 PRIMARY KEY (id) ENABLE);

  create trigger t1_trigger
  before insert on AUDITLOGS
  for each row
   begin
     select t1_seq.nextval into :new.id from dual;
   end;

only I have to just change the table name (AUDITLOGS) with your table name and new.id with new.column_name

FUNCTION UNIQUE2(
 seq IN NUMBER
) RETURN VARCHAR2
AS
 i NUMBER := seq;
 s VARCHAR2(9);
 r NUMBER(2,0);
BEGIN
  WHILE i > 0 LOOP
    r := MOD( i, 36 );
    i := ( i - r ) / 36;
    IF ( r < 10 ) THEN
      s := TO_CHAR(r) || s;
    ELSE
      s := CHR( 55 + r ) || s;
    END IF;
  END LOOP;
  RETURN 'ID'||LPAD( s, 14, '0' );
END;

oracle has sequences AND identity columns in 12c

http://www.oracle-base.com/articles/12c/identity-columns-in-oracle-12cr1.php#identity-columns

I found this but not sure what rdb 7 is http://www.oracle.com/technetwork/products/rdb/0307-identity-columns-128126.pdf

Maybe just try this simple script:

http://www.hlavaj.sk/ai.php

Result is:

CREATE SEQUENCE TABLE_PK_SEQ; 
CREATE OR REPLACE TRIGGER TR_SEQ_TABLE BEFORE INSERT ON TABLE FOR EACH ROW 

BEGIN
SELECT TABLE_PK_SEQ.NEXTVAL
INTO :new.PK
FROM dual;
END;