How to add foreign key value in insert query - mysql - CodeIgniter - mysql

Question

I have the following insert query:
$salarystuff = array('salary' => $salary, 'from_date' => $salary_from_date, 'to_date' => $salary_to_date);
$this->db->insert('salaries', $salarystuff);
The salary table has columns: emp_no| salary| from_date| to_date (I'm using the database available from dev.mysql.com.
But it gives me an error 1452 saying foreign key constraint. How do I reference to the key value in the other table to be able to insert into this table?
This is the error message:
Cannot add or update a child row: a foreign key constraint fails
(employees.salaries, CONSTRAINT salaries_ibfk_1 FOREIGN KEY
(emp_no) REFERENCES employees (emp_no) ON DELETE CASCADE)
INSERT INTO salaries (salary, from_date, to_date) VALUES
('1000000', '2012-12-27', '2013-01-16')
Thank you
edit: I'm trying the following
First I create the record in the employees table using this function:
function add_emp($firstname,$lastname,$gender,$date_of_birth,$jobtitle,$dept,$hiredate)
{
$data = array( 'first_name' => $firstname,
'last_name' => $lastname,
'gender' => $gender,
'birth_date' => $date_of_birth,
'hire_date' => $hiredate);
$this->db->trans_start();
$this->db->insert('employees', $data);
$this->db->trans_complete();
if ($this->db->trans_status() === FALSE)
{
$msg = "Adding the new employee failed.";
return $msg;
}
else
{
$msg = "Successfully Added Employee.";
return $msg;
}
}
and then in another function I add the salary:
function add_salary($firstname,$lastname,$gender,$date_of_birth,$jobtitle,$dept,$hiredate,$salary, $salary_from_date,$salary_to_date)
{
$this->db->select('emp_no');
$this->db->from('employees');
$this->db->where('first_name', $firstname);
$this->db->where('last_name', $lastname);
$this->db->where('gender', $gender);
$this->db->where('hire_date', $hiredate);
$this->db->where('birth_date', $date_of_birth);
$this->db->limit(1);
$selected_employee = $this->db->get();
$salarystuff = array('emp_no' => $selected_employee, 'salary' => $salary, 'from_date' => $salary_from_date, 'to_date' => $salary_to_date);
$this->db->insert('salaries', $salarystuff);
}
both of which are in the model. Then in the controller I call both functions:
$employee_insert = $this->user->add_emp($firstname,$lastname,$gender,$date_of_birth,
$jobtitle,$dept, $hiredate);
$salarythings = $this->user->add_salary($firstname,$lastname,$gender,$date_of_birth,$jobtitle,$dept,$hiredate,$salary, $salary_from_date,$salary_to_date);
But I get an error because there is no value in the emp_no field...I think it might be the line:
$selected_employee = $this->db->get();
$salarystuff = array('emp_no' => $selected_employee,
My error message is:
Object of class CI_DB_mysql_result could not be converted to string

Answer 1

The problem is you are trying to insert into the salaries table, but you aren't specifying what employee the salary record is for. You would need to provide a value for the emp_no column that is in the employees table.
ETA:
Glad you posted more code - what you should do is modify your add_emp function so that it returns the id of the employee that was created (I'm assuming here that emp_no is and auto-increment column in your database). Like so:
function add_emp($firstname,$lastname,$gender,$date_of_birth,$jobtitle,$dept,$hiredate)
{
$data = array( 'first_name' => $firstname,
'last_name' => $lastname,
'gender' => $gender,
'birth_date' => $date_of_birth,
'hire_date' => $hiredate);
$this->db->trans_start();
$this->db->insert('employees', $data);
$this->db->trans_complete();
if ($this->db->trans_status() === FALSE)
{
//$msg = "Adding the new employee failed.";
//return $msg;
return -1; // indicates failure
}
else
{
//$msg = "Successfully Added Employee.";
//return $msg;
return $this->db->insert_id();
}
}
Note that the code that calls add_emp will need to change a bit to look at the return value as an integer instead of a message now, but now you have the id of the employee and you can use that in your add_salary function instead of having to pass in all that other data, like so:
function add_salary($emp_no,$salary, $salary_from_date,$salary_to_date)
{
$salarystuff = array('emp_no' => $emp_no, 'salary' => $salary, 'from_date' => $salary_from_date, 'to_date' => $salary_to_date);
$this->db->insert('salaries', $salarystuff);
}
So the code to add an employee and their salary would be something like this:
$emp_no = add_emp([Your parameters]);
if ( $emp_no > 0 ) {
add_salary($emp_no, [other parameters]);
} else {
// Show some error message that the employee creation failed.
}
EDIT AGAIN:
If you ignore my advice above, the simple answer to why you are getting an error is because $selected_employee is a result set and not an actual employee number. You would need to change that code like so:
$selected_employee = $this->db->get();
$result = $selected_employee->result();
$emp_no = $result[0]->emp_no;
$salarystuff = array('emp_no' => $emp_no, 'salary' => $salary, 'from_date' => $salary_from_date, 'to_date' => $salary_to_date);
$this->db->insert('salaries', $salarystuff);