sql从开始删除

Question

无论如何，我可以将表中允许的行数限制为40，然后在添加41st时，表删除第一个？

Answer 1

Yes, you could do this with a trigger. What RDMS are you using?

Answer 2

CREATE TABLE animals (
 id MEDIUMINT NOT NULL AUTO_INCREMENT,
 name CHAR(30) NOT NULL,
 PRIMARY KEY (id)
);

-- if this is 41st record, ...
-- the statement below will delete the id with 1, and so forth
insert into animals(name) values('wolverine'); 
delete from animals where id <=  LAST_INSERT_ID() - 40;