if i have table employee with employee_id as a primary key
how can i assign the primary key to the columns firstname and lastname?
table structure is something like this :
employee_id int not null, firstname varchar(20) not null, lastname varchar(20) not null
the problem is that there is a foreign key in other table that referes to the table employee , so when i try to delete the primary key i get error said i can't delete coze it refers to other table ...
if i create foreign key by this way
alter table le_order
add constraint fk_salesman foreign key (Salesman_id) REFERENCES employee
how can i update this statement and add
on delete set null
and to set it to null is that correct for first problem
note : sorry my english isn't good , if you please excuse me.