Why isn't the primary key incrementing ON DUPLICATE? - mysql

Question

I have the following TEACHER table that has the following schema:
create table TEACHER
(
TEACHERID int not null auto_increment,
FIRST_NAME varchar(20) not null,
SURNAME varchar(20) not null,
primary key (TEACHERID)
);
I have multiple inserts with the same first name and surname of teacher that I wish to omit. The schema is given and I don't plan on modifying it.
I try to execute dynamically in my program the following query but the TEACHERID is not incrementing, actually no new fields with new first name and last name are added, there is only one field that is constantly being updated.
Here is my query:
INSERT INTO TEACHER set ? ON DUPLICATE KEY UPDATE FirstName = ?, LastName = ?'
with the ? are defined as follows: values: [set, professor.name, professor.sname ]
where a set is defined as follows:
set = {
FirstName: professor.name,
LastName: professor.sname
}
How do I get the primary key to increment on each duplicate, without actually adding that duplicate?
Thank you

Answer 1

You are getting that behavior cause you are using ON DUPLICATE KEY UPDATE. If you really want to insert the duplicate record then just perform a INSERT statement like
INSERT INTO TEACHER VALUES('test','test')
How do I get the primary key to increment on each duplicate, without
actually adding that duplicate?
Sorry that's not possible at-least with auto increment. You will then have to have your own primary key and on every insert do some manipulation through a before insert trigger. Something like
create table TEACHER
(
TEACHERID int not null primary key,
create trigger trg_binsert
on TEACHER before insert
for each row
begin
if(new.FIRST_NAME = FIRST_NAME and new.SURNAME = SURNAME)
update TEACHER
SET TEACHERID = TEACHERID + 1
WHERE new.FIRST_NAME = FIRST_NAME
and new.SURNAME = SURNAME;
end if
end
Though, not sure why you want to do that and won't recommend as well.