SQL - Select all items in a radius - sql

Question

I'm trying to make a SQL statement which provides me a list with candidates within a certain area. I like to make a selection based on (A) location of a job and (B) location of a candidate. The SQL statement needs to work on a MariaDB server.
I did the homework but can't figure out how to get this done. I believe the code needs to be something like this. But, i'm not quite sure how this works.
DESCRIPTION
Input: Job-id, radius
Calls: candidate-table (id’s, location), job-table (id’s, location)
Output: list of candidates within a radius
Implementation
DELIMITER //
CREATE PROCEDURE calc_distance (IN job_id_var data_type, IN radius_var FLOAT, OUT cand_list)
SQL SECURITY INVOKER
COMMENT ‘this code…’
BEGIN
/* Table with candidate-job combination and relevant characteristics (distance between the two) */
DECLARE #result1 TABLE (job_id INT, cand_id INT, job_x DOUBLE, job_y DOUBLE, cand_x DOUBLE, cand_y DOUBLE, dist DOUBLE)
SET #job_x = (SELECT job_x FROM job_table WHERE job_id = job_id_var)
SET #job_y = (SELECT job_y FROM job_table WHERE job_id = job_id_var)
INSERT INTO #result1 (cand_id, cand_x, cand_y)
SELECT a, b, c
FROM cand_table;
UPDATE #result1
SET job_id = job_id_var, job_x = #job_x, job_y = #job_y, dist = SQRT(POW(cand_x - job_x,2) + POW(cand_y - job_y,2))
SELECT * as cand_list
FROM #result
WHERE dist <= radius_var
END //
DELIMITER ;

Answer 1

I don't think this works: DECLARE #result1 TABLE ... -- In general you cannot do substitutions without prepare and execute.
The entire procedure can be done in a single SELECT. In general, you should strive for such. This is because SQL thinks in performing things on sets (tables), not a single thing at a time.
OUT cand_list -- OUT values can only be scalars. However the entire procedure can produce effectively the same as a SELECT, namely a bunch of rows and columns. So the entire Stored Proc becomes only:
SELECT ...
FROM job_table
WHERE Distance(job_x, job_y, cand_x, cand_y) < radius_var
If you want, you could tack on ORDER BY Distance(...) to get the nearest first.
Well, OK, now we need to define a simple Stored Function named Distance that takes two pairs of x and y, returning a FLOAT.
Caution: x and y work for some situations, but they don't work well for latitude and longitude. Longitudes need to be divided by cos(latitude) to adjust.

Answer 2

Thanks! I found my answer in this:
SELECT contractor.id,
(3959 * acos( cos( radians( 51.5318464 ) ) * cos( radians( address.latitude ) )
* cos( radians( longitude ) - radians( 4.4287569) ) + sin( radians( 51.5318464 ) ) * sin( radians( latitude ) ) ) )
AS distance
FROM address
INNER JOIN contractor on address.id = contractor.address_id
HAVING distance < 20
ORDER BY distance