How do I prevent removal on assigned objects?

See more:

Javascript

SQL

When the user selects to delete a department or location, then the system should check against the database to see if that entry is used in other tables (ie personnel assigned to that department) and, if so, should prevent removal.

What's the best way to do it?

See my code:

<div class="col d-flex justify-content-center">

	<div class="btn btn-xs btn-primary5" id="confirmButton" style="display: inline; float: right;" onclick="toggleConfirmDep('Remove', 'removeDepartment()')"></div>

</div>

function removeDepartment() {

    let departmentName = $('#removeDepartmentDepartment').val()

    $.getJSON(`php/getAllDepartments.php`, function (departments) {

        let departmentID = departments.data.filter(dep => dep.name == departmentName)[0].id

        $.ajax({

            data: {
                'id': departmentID
            },
            url: 'php/deleteDepartmentByID.php', 
            dataType: 'json',

            success: function(data) {

                $('#removeDepartmentDepartment').find('option:eq(0)').prop('selected', true);
    
            }

        })

    }); 

}

function toggleConfirmDep(message, func) {
    
    if (!event) var event = window.event;
    event.cancelBubble = true;
    if (event.stopPropagation) event.stopPropagation();


    employeeID = $(event.target).closest(".buttons").siblings("form").find("#id").text();

    if ($('#confirmDep').css('display') == "none") {

        $('#confirmDep').show()
        $('#depQuestion').show()
        $('#depResponse').hide()

        let addOrRemove = capitalizeFirstLetter(message.split(" ")[0])
        addOrRemove == "Add" ? addOrRemove += "ed" : addOrRemove += "d"

        $('#depMessage').text(message)
        $('#depButton').attr('onClick', `
            ${func.toString()};
            $('#depQuestion').hide()
            $('#depResponse').show()
            $('#depResponseMessage').text('${addOrRemove}')
            setTimeout(function(){
                $('#confirmDep').hide();
                
                $('#profilePage').hide();
                
                window. location. reload(1);
                
            }, 1500);
            
        `)

    } else {
        
        $('#confirmDep').css('display', 'none')

    }

}

<?php

	// remove next two lines for production
	
	ini_set('display_errors', 'On');
	error_reporting(E_ALL);

	$executionStartTime = microtime(true);

	include("config.php");

	header('Content-Type: application/json; charset=UTF-8');

	$conn = new mysqli($cd_host, $cd_user, $cd_password, $cd_dbname, $cd_port, $cd_socket);

	if (mysqli_connect_errno()) {
		
		$output['status']['code'] = "300";
		$output['status']['name'] = "failure";
		$output['status']['description'] = "database unavailable";
		$output['status']['returnedIn'] = (microtime(true) - $executionStartTime) / 1000 . " ms";
		$output['data'] = [];

		mysqli_close($conn);

		echo json_encode($output);

		exit;

	}	

	// $_REQUEST used for development / debugging. Remember to cange to $_POST for production

	$query = 'DELETE FROM department WHERE id = ' . $_REQUEST['id'];

	$result = $conn->query($query);
	
	if (!$result) {

		$output['status']['code'] = "400";
		$output['status']['name'] = "executed";
		$output['status']['description'] = "query failed";	
		$output['data'] = [];

		mysqli_close($conn);

		echo json_encode($output); 

		exit;

	}

	$output['status']['code'] = "200";
	$output['status']['name'] = "ok";
	$output['status']['description'] = "success";
	$output['status']['returnedIn'] = (microtime(true) - $executionStartTime) / 1000 . " ms";
	$output['data'] = [];
	
	mysqli_close($conn);

	echo json_encode($output); 

?>

What I have tried:

I have tried the seal object assigned object database javascript but it does not work.