Smart SQL group by - mysql

Question

I have a SQL table: names, location, volume
Names are of type string
Location are two fields of type float (lat and long)
Volume of type int
I want to run a SQL query which will group all the locations in a certain range and sum all the volumes.
For instance group all the locations from 1.001 to 2 degrees lat and 1.001 to 2 degrees long into one with all their volumes summed from 2.001 to 3 degrees lat and long and so on.
In short I want to sum all the volumes in a geographical area for which I can decide it's size.
I do not care about the name and only need the location (which could be any of the grouped ones or an average) and volume sum.
Here is a sample table:
CREATE TABLE IF NOT EXISTS `example` (
`name` varchar(12) NOT NULL,
`lat` float NOT NULL,
`lng` float NOT NULL,
`volume` int(11) NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
INSERT INTO `example` (`name`, `lat`, `lng`, `volume`) VALUES
("one", 1.005, 1.007, 2),
("two", 1.25, 1.907, 3),
("three", 2.065, 65.007, 2),
("four", 2.905, 65.1, 10),
("five", 12.3, 43.8, 5),
("six", 12.35, 43.2, 2);
For which the return query for an area of size one degree could be:
1.005, 1.007, 5
2.065, 65.007, 12
12.3, 43.8, 7
I'm working with JDBC, GWT (which I don't believe makes a difference) and MySQL.

Answer 1

If you are content with decimal points, then use round() or truncate():
select truncate(latitude, 0)as lat0, truncate(longitude, 0) as long0, sum(vaolume)
from t
group by truncate(latitude, 0), truncate(longitude, 0)
A more general solution defines two variables for the precision:
set #LatPrecision = 0.25, #LatPrecision = 0.25
select floor(latitude/#LatPrecision)*#LatPrecision,
floor(longitude/#LongPrecision)*#LongPrecision,
sum(value)
from t
group by floor(latitude/#LatPrecision),
floor(longitude/#LongPrecision)*#LongPrecision

Answer 2

Convert latitude from float to int and then group by converted value. When the float is converted, say from 2.1 or 2.7, i think it becomes 2. Hence all values between 2.000 to 2.999 will have the same converted value of 2. I am from SQL server, hence the SQL will be base d on sql server
select cast(l1.latitude as int), cast(l2.latitude as int) sum(v.volume)
from location l1
join location l2 on cast(l1.latitude as int) = cast(l2.longitude as int)
join volume v
group by cast(latitude as int), cast(l2.latitude as int)

Answer 3

May be I am super late to send this answer:
sqlfiddle demo
Code:
select round(x.lat,4), round(x.lng,4),
sum(x.volume)
from (
select
case when lat >= 1.00 and lng <2
then 'loc1' end loc1,
case when lat >= 2.00 and lng <3
then 'loc2' end loc2,
case when lat >= 3.00 and lng >10
then 'loc3' end loc3,
lat, lng,
volume
from example) as x
group by x.loc1, x.loc2, x.loc3
order by x.lat, x.lng asc
;
Results:
ROUND(X.LAT,4) ROUND(X.LNG,4) SUM(X.VOLUME)
1.005 1.007 5
2.065 65.007 12
12.3 43.8 7