Oracle implements PRIMARY key auto-increment

Because Oracle sets the primary key is not automatically incremented, you must use sequences and triggers to complete the increment of the primary key

1. Set up a data sheet

CREATE TABLE Test_increase (
UserID Number (primary key,/* Establish PRIMARY KEY */
Username VARCHAR2 (20)
);

2. Create an auto-grow sequence

CREATE SEQUENCE testincrease_sequence
INCREMENT by 1--add a few each time
Start with 1-counting starting from 1
Nomaxvalue--Do not set the maximum value
Nocycle--keep accumulating, not looping
CACHE 10;

3. Create a Trigger

CREATE TRIGGER Test_increase before
Insert on Test_increase for each ROW
Begin
Select Testincrease_sequence.nextval Into:New.userid from dual;
End

Execute the above 3-step statement

Oracle implements PRIMARY key auto-increment