Example tutorial for creating a self-added primary key in an Oracle database _oracle

When designing a database table, it was found that Oracle did not have a set of self-adding primary keys, and Google learned that Oracle itself does not support the Sequence key, which needs to be implemented through sequences (Trigger) and triggers.
CREATE TABLE Student

Create Table Student ( 
 ID number () primary key, the 
 name Varchar2 ( 
 3) 
 that implements the ID by sequence and trigger, Sex number (1) 
) 

Create a sequence sequence

Create Sequence seq_student 
minvalue 1 
maxvalue 99999999999999999999 start with 
1   --Starting 
from 1 Increment by 1--increment to 1 
cache 0 Order 
; 

Creating triggers Trigger

Create or Replace Trigger student_autoincrement 
before Insert on STUDENT for each 
Row 
, New.id is NULL 
Begin 
Select seq_student. Nextval INTO:NEW.ID from DUAL; 
End; 

Note the point:

1: A sequence can be shared by multiple tables.

2: The number of sequence generated by multiple tables is always continuous and will not start again.

3: Remove sequence If no longer in use.

SELECT * from DAYSBFJ. DAYS_CARD_UPDATE3 ORDER BY ID ASC
--alter table DAYSBFJ. Days_card_update3 Add Source_flag varchar2 (2);
--create sequence days_card_update2_seq_id minvalue 1 maxvalue 999999999 start with 1;
--update DAYSBFJ. Days_card_update2 Set id = days_card_update2_seq_id.nextval;
--update DAYSBFJ. Days_card_update3 Set source_flag = ' 2 '

Another example:

Create a new table with missing primary key

CREATE TABLE Test1 (name1 varchar2 (), City Varchar2 (40));

--Inserting data

INSERT into test1 values (' name1 ', ' Nanjing ');
INSERT into test1 values (' name1 ', ' Nanjing ');
INSERT into test1 values (' name2 ', ' nanjing1 ');
INSERT into test1 values (' Name3 ', ' nanjing2 ');
INSERT into test1 values (' name4 ', ' nanjing3 ');
INSERT into test1 values (' name5 ', ' Nanjing4 ');
INSERT into test1 values (' Name6 ', ' nanjing5 ');
INSERT into test1 values (' Name7 ', ' Nanjing6 ');
INSERT into test1 values (' Name8 ', ' Nanjing7 ');
INSERT into test1 values (' name9 ', ' Nanjing8 ');
INSERT into test1 values (' Name10 ', ' nanjing9 ');
INSERT into test1 values (' Name10 ', ' nanjing9 ');
INSERT into test1 values (' name12 ', ' nanjing11 ');
INSERT into test1 values (' name13 ', ' nanjing12 ');
INSERT into test1 values (' name14 ', ' nanjing13 ');
Commit

--Increase primary Key ID

ALTER TABLE TEST1 Add ID number (10);

--set sequence to make ID self-increasing

Create sequence seq_id
 minvalue 1
 maxvalue 999999999
 start with 1;

--Set the value of the ID to sequence

Update test1 set id=seq_id.nextval;
Commit

--Set ID as primary key

ALTER TABLE TEST1
 add constraint Pk_test1 primary key (ID);
 
Select Id,name1,city from TEST1;