Question

I have a table like the following:-

Table: deals
+----+-------+----------+----------+------------+
| ID |  name | latitude | longitude|  end_date  |
|----+-------+----------+----------+------------+
|  1 | pizza |    10.5  |   -10.5  | 2012-12-12 |
|  2 | pizza |    11.5  |   -10.5  | 2012-12-12 |
|  3 | jelly |    21.5  |   -10.5  | 2012-12-12 |
|  4 | jelly |    23.5  |   -10.5  | 2012-12-12 |
|  5 | lily  |    19.5  |   -10.5  | 2012-12-12 |
+----+-------+----------+----------+------------+

I’m using the latitude and longitude to find the distance to that person. But I need result to be DISTINCT based on name. I also need to sort the results by the distance I calculated and apply the limit 0,3.

The query I’m currently using is”-

SELECT *,
   ( 6371 * Acos(Cos(Radians(9.939625)) * Cos(Radians(lat)) * Cos(
                               Radians(lng) - Radians(76.259498)) +
                          Sin(Radians(9.939625)) * Sin(Radians(lat))) ) AS
   distance
FROM   deals
WHERE  1
   AND end_date >= Now()
HAVING distance < 20000
ORDER  BY id DESC,
      distance
LIMIT  0, 3;  

So in short, what I need is:-

1. List of the closest deals (sorted by distance)
2. Apply distinct to name (so that both pizza and jelly will appear only once)

Answer 1

You’ll want to apply MIN to get the minimum distance per name, GROUP BY name (which gives one result per name) and ORDER BY distance first and id later;

SELECT *,
   MIN( 6371 * Acos(Cos(Radians(9.939625)) * Cos(Radians(latitude)) * Cos(
                               Radians(longitude) - Radians(76.259498)) +
                          Sin(Radians(9.939625)) * Sin(Radians(latitude))) ) 
AS distance
FROM   deals
WHERE  end_date >= Now()
GROUP BY name
ORDER  BY distance, id DESC

I should add that this query may be ok for your case but isn’t generally very useful, since if you want to know for example the latitude and longitude of the closest pizza place, you’ll need an entirely different query.