Oracle column self-increment implementation

1.sequence+trigger enables Oracle column self-increment
CREATE SEQUENCE sequence Name
[INCREMENT by N]
[START with N]
[{Maxvalue/minvalue n| Nomaxvalue}]
[{cycle| Nocycle}]
[{CACHE n| NOCACHE}];
Create a test table
[Email protected] Cdb> CREATE TABLE TEST (
2 ID Number (Ten) is not NULL,
3 DESCRIPTION VARCHAR2 () not NULL,
4 CONSTRAINT test_pk PRIMARY KEY (ID)
5);

Table created.

elapsed:00:00:00.14
[Email protected] cdb> CREATE SEQUENCE test_seq;

Sequence created.

elapsed:00:00:00.02

elapsed:00:00:00.38
[Email protected] cdb> CREATE OR REPLACE TRIGGER Test_before_insert
2 before INSERT on test
3 for each ROW
4 BEGIN
5 SELECT Test_seq. Nextval INTO:new.id from dual;
6 END;
7/

Trigger created.

elapsed:00:00:00.12
[Email protected] Cdb> INSERT into TEST (DESCRIPTION) VALUES (' Do not specify ID ');

1 row created.

elapsed:00:00:00.08
[Email protected] Cdb> INSERT into TEST (ID, DESCRIPTION) VALUES (Test_user. Dept_seq. Nextval, ' specify ID ');
INSERT into TEST (ID, DESCRIPTION) VALUES (Test_user. Dept_seq. Nextval, ' Specify ID ')
*
ERROR at line 1:
Ora-02289:sequence does not exist

elapsed:00:00:00.01
[Email protected] Cdb> INSERT into TEST (ID, DESCRIPTION) VALUES (test_seq. Nextval, ' specify ID ');

1 row created.

elapsed:00:00:00.01
[Email protected] Cdb> SELECT * from TEST;

    ID DESCRIPTION

     1 不指定ID     3 指定ID

elapsed:00:00:00.03
2.DEFAULT Values Using Sequences
[Email protected] Cdb> INSERT into TEST (description) VALUES (' description only ');

1 row created.

elapsed:00:00:00.01
[Email protected] Cdb> INSERT into TEST (ID, description) VALUES (999, ' id=999 and description ');

1 row created.

elapsed:00:00:00.00
[Email protected] Cdb> INSERT into TEST (ID, description) VALUES (NULL, ' id=null and description ');

1 row created.

elapsed:00:00:00.01
[Email protected] Cdb> SELECT * from test;

    ID DESCRIPTION

     4 DESCRIPTION only   999 ID=999 and DESCRIPTION       ID=NULL and DESCRIPTIONElapsed: 00:00:00.02

[Email protected] Cdb> CREATE TABLE TEST (
2 ID Number (Ten) DEFAULT on NULL test_seq. Nextval,
3 DESCRIPTION VARCHAR2 () not NULL
4);

Table created.

elapsed:00:00:00.02
[Email protected] Cdb> INSERT into TEST (description) VALUES (' description only ');

1 row created.

elapsed:00:00:00.01
[Email protected] Cdb> INSERT into TEST (ID, description) VALUES (999, ' id=999 and description ');

1 row created.

elapsed:00:00:00.01
[Email protected] Cdb> INSERT into TEST (ID, description) VALUES (NULL, ' id=null and description ');

1 row created.

elapsed:00:00:00.01
[Email protected] Cdb> SELECT * from test;

    ID DESCRIPTION

     5 DESCRIPTION only   999 ID=999 and DESCRIPTION     6 ID=NULL and DESCRIPTION

elapsed:00:00:00.02
3. Look at an article inside

Oracle column self-increment implementation