Question

I’m trying to execute this query:

SELECT  `venues` . * 
FROM  `venues` 
WHERE  `lat` >= 39.847991180331
AND  `lng` >= -86.332592054637
AND  `lat` <= 40.137846252794
AND  `lng` <= -85.954901904578
LIMIT 0 , 30

Here is the table structure of the lat and lng fields and a sample row, it should be returning AT LEAST 1 row

lng decimal(65,15)                              
lat decimal(65,15)

Name                  Lng                   Lat
Ambre Blends Studio   -86.143746979607530   39.875314973898870

However when I execure the above query it returns no rows. What’s the problem here?

Answer 1

I’m always circumspect about floating point equality and inequality operations and MySQL has had a history of problems in the past with this sort of thing (I’m not sure which version you’re using but there were some changes made around 503/505).

The first thing I would do is debug the actual statement. Start with:

select venues.* from venues
 where name like 'Ambre%'

and ensure you only get one row (you may have to tweak the where clause if there’s lots of rows starting with Ambre).

Then add the other subclauses one at a time until the row doesn’t appear. The first would be:

select venues.* from venues
 where name like 'Ambre%'
   and lat >= 39.847991180331

Once you establish which condition is causing the select to fail, you can start looking into why.