How to get location from latitude and longitude in T-SQL? - sql

Question

I have a mapping table of locationId along with their center latitude and center longitude value like below-
| Location Id | Center_lat | Center_long |
|-------------|------------|-------------|
| 1 | 50.546 | 88.344 |
| 2 | 48.546 | 86.344 |
| 3 | 52.546 | 89.344 |
I have another table where I am getting continuous location data with latitude and longitude for user like below -
+---------+------------+-------------+
| User Id | Center_lat | Center_long |
+---------+------------+-------------+
| 101 | 50.446 | 88.314 |
| 102 | 48.446 | 86.314 |
| 103 | 52.446 | 89.314 |
+---------+------------+-------------+
I want to get the locationId of all users if their latitude and longitude values lies within 1000 meters of lat-long values corresponding to location id. How can I get it done in T-SQL?
Final table should like below -
+---------+------------+-------------+------------+
| User Id | Center_lat | Center_long | LocationId |
+---------+------------+-------------+------------+
| 101 | 50.546 | 88.344 | 1 |
| 102 | 48.546 | 86.344 | 2 |
| 103 | 52.546 | 89.344 | 3 |
+---------+------------+-------------+------------+

Answer 1

You can use convert the latitude/longitude pairs to geography objects, and then use stdistance():
select u.*, l.location_id
from users u
inner join locations l
on geography::point(u.center_lat, u.center_long, 4326).stdistance(geography::point(l.center_lat, l.center_long, 4326)) < 1000
Note that it would be much more efficient to store this information as points to start with.