error in php and mysql, Error: You have an error in your SQL syntax; check the manual that cor Options

[jobedsno]

I have Error: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '' at line 13 and i dont know how and where did i get that wrong

<?php

function retrieve(){
include 'connection.php';
//$result = "SELECT candidate_id, first_name,middle_name,last_name,sex FROM candidates ";

$result = "SELECT
candidates.candidate_id,
education_level,
english_level,
experience_time,
district
FROM candidates
JOIN education_quali ON candidates.candidate_id = education_quali.candidate_id
LEFT JOIN employ_history ON candidates.candidate_id = employ_history.candidate_id
WHERE candidates.candidate_id = (
SELECT candidate_id
FROM candidate_job
WHERE candidate_job.candidate_job = 'sales' ";

$query = mysqli_query($db_connection, $result)
or die("Error: ".mysqli_error($db_connection));