mysql - SQL Cannot add or update a child row: a foreign key constraint -

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create table employee( ->  emp_no          int(4), ->  emp_fname       varchar(50), ->  emp_lname     varchar(50), ->  job_class               varchar(4), ->  primary key     (emp_no), ->  foreign key (job_class) references job (job_class) ->  );

query ok, 0 rows affected (0.09 sec)

create table project( ->  pro_no       int(4), ->  pro_name                varchar(50), ->  pro_leader     varchar(50), ->  emp_no       int(4), ->  primary key (pro_no), ->  foreign key (emp_no) references employee (emp_no) ->  );

query ok, 0 rows affected (0.23 sec)

create table assign( ->  pro_no       int(4), ->  emp_no          int(4), ->  job_class    varchar(4), ->  assign_hours       decimal(6,2), ->  total_charge        decimal(6,2), ->  primary key (pro_no, emp_no), ->  foreign key (pro_no) references project (pro_no), ->  foreign key (emp_no) references employee (emp_no) ->  );

query ok, 0 rows affected (0.08 sec)

insert employee (emp_no, emp_fname, emp_lname, job_class) values ('101', 'john','new','dd');

error 1452 (23000): cannot add or update child row: foreign key constraint fails
(o_m_m.employee, constraint employee_ibfk_1 foreign key (job_class) references job (job_class))

can please me, sql working fine

i missing -> foreign key (job_class) references job (job_class) in employee added , populated

now receive error

foreign key relationships involve parent table holds central data values, , child table identical values pointing parent. foreign key clause specified in child table.

it reject insert or update operation attempts create foreign key value in child table if there no matching candidate key value in parent table.

perhaps, attempting insert foreign key value in child table doesn't exist in parent table.

courtesy: using foreign key constraints


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