Primary Key Increase by Trigger

Oracle Create Table：

CREATE TABLE TAB(
  ID NUMBER(10) NOT NULL PRIMARY KEY,
  NAME VARCHAR(19) NOT NULL
);

Drop table when exists:

BEGIN
  EXECUTE IMMEDIATE 'DROP TABLE TAB';
EXCEPTION
  WHEN OTHERS THEN
    IF SQLCODE != -942 THEN
       RAISE;
    END IF;
END;

Create sequence as id:

CREATE SEQUENCE ID_SEQ_TAB
START WITH 1
INCREMENT BY 1
MINVALUE 1
NOMAXVALUE
NOCACHE;

Drop sequence when exists:

BEGIN
  EXECUTE IMMEDIATE 'DROP SEQUENCE ID_SEQ_TAB';
EXCEPTION
  WHEN OTHERS THEN
    IF SQLCODE != -2289 THEN
       RAISE;
    END IF;
END;

Create trigger:

CREATE OR REPLACE TRIGGER ID_TRI_TAB
BEFORE INSERT
ON TAB
FOR EACH ROW
WHEN(NEW.ID IS NULL)
BEGIN
SELECT ID_SEQ_TAB.NEXTVAL INTO :NEW.ID FROM DUAL;
END; 

Insert into table:

Insert into table_name (column_name...) values(values...)

Select column names of a table:

select column_name from user_tab_columns
where table_name = 'YOUR TABLE NAME HERE';

ps:

• dual:

A mystery table in Oracle, You can select many things from this table:

Select a_squence_name.nextval from dual

• Select into from:

A copy operation on oracle.You can use it like this:

SELECT * INTO new_table_name [IN externaldatabase] FROM old_tablename