Question

i have a query that returns some users related to a specific user (Bob).

I need to retrieve the nearest records, meaning, i must return users whose ID column is near Bob’s ID.

For example:

         ID

Tom      5
Mike     8
Bob      10
Jack     12
Brian    13

The query:

SELECT users.* FROM users
INNER JOIN neighboors on neighboors.neighboor_id = users.id #ignore this join, just to exemplify
WHERE neighboors.user_id = 10 # bobs id
ORDER BY something
LIMIT 3 # i want to return only the 3 nearest users (according to the table above:mike, jack and brian)

How can i achieve this?

updated

the logic is, users can plant trees, each tree has an specie. The query should return users that have planted the same tree specie.

And why is important order by proximity of id? the client want this way 🙂 there is no other reason.

Answer 1

Try with this, should do what you need :

SELECT users.* FROM users
INNER JOIN neighboors ON neighboors.neighboor_id = users.id
WHERE neighboors.user_id = 10 
ORDER BY ABS(neighboors.user_id - 10)
LIMIT 3

The ABS function in this case it is used to calculate the “distance” from user_id selected value (the value filtered by the WHERE … ).

To obtain better performance on large tables you have to index(if not yet) the column : neighboors.user_id .