How to create id with AUTO_INCREMENT on Oracle?

Question

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?

Answer 1

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));

Answer 2

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>>
)

Answer 3

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;
/

Answer 4

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.

Answer 5

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

Answer 6

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.

The following article explains how to use it:

Identity columns - A new entry in Oracle Database 12c

Answer 7

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.

Answer 8

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.

Answer 9

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

Answer 10

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;
/

Answer 11

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;

Answer 12

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;

Answer 13

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;

Answer 14

  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

Answer 15

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

Answer 16

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;