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Today, I will talk to you about how Oracle triggers achieve the primary key self-increasing effect, which may not be well understood by many people. in order to make you understand better, the editor has summarized the following content for you. I hope you can get something according to this article.

The function of trigger

A trigger acts like an interceptor. Intercept some DML operations (insert/update/delete/select) against the database, and operate those that meet the business requirements. Operations that do not meet the requirements can be blocked by throwing an exception.

To put it bluntly, it is data confirmation (after) and security check (before). In addition, triggers are not targeted at select operations.

1. First create the table testUser

Oracle is set to be size-insensitive, so the table name is concise and concise.

CREATE TABLE testUser (id NUMBER (11) primary key, name VARCHAR (50)

two。 Create a sequence with a minimum of 1, a maximum of 99999999, an initial value of 1, and a step size of 1

Sequence name is customarily named for a certain table: seq_ table name

CREATE sequence seq_testUser minvalue 1 maxvalue 99999999 START WITH 1 INCREMENT BY 1 nocache ORDER

3. Create trigger

The trigger is based on sequence, so it is customary to name it: trg_sequence name

CREATE OR REPLACE TRIGGER trg_seq_testUser BEFORE INSERT ON testUser FOR EACH ROWBEGIN SELECT seq_testUser.nextval INTO: new.id FROM dual; END

4. Insert a piece of data

Insert into testUser (username) values ('Qiang 0'); insert into testUser (username) values ('Qiang 1'); insert into testUser (username) values ('Qiang 2')

5 query results

Select * from testUser after reading the above, do you have any further understanding of how Oracle triggers achieve the self-increasing effect of primary keys? If you want to know more knowledge or related content, please follow the industry information channel, thank you for your support.

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