How to optimized my code in Mysql? - mysql

Question

I hava three tables called t_asset,t_device and t_asset_device.The relationship between t_asset and the t_device is multiple pairs.Each table column is :
t_asset :id , asset_name,asset_code,create_time,creator
t_device:id, device_name,device_code,latitude,longitude,create_time,creator
t_assets_device:id,asset_id,device_id,create_time,creator
Now I want to get all the t_asset and the latitude,longitude of the first device,So I write the code and function like these:
fun_getLatitudeByAssetId(`assetId` varchar(50)){
BEGIN
declare v_latituede DECIMAL(10,5) DEFAULT(-1) ;
select latitude into v_latituede
from t_device tDevice
inner join t_assets_device tAssetsDevice
on tAssetsDevice.asset_id=assetId and
tDevice.id=tAssetsDevice.device_id
and tDevice.latitude!=-1
ORDER BY tDevice.id desc
limit 0,1;
return v_latituede;
END
}
fun_getLongititueByAssetId(`assetId` varchar(50)){
BEGIN
declare v_longititue DECIMAL(10,5) DEFAULT(-1) ;
select longititueinto v_longititue
from t_device tDevice
inner join t_assets_device tAssetsDevice
on tAssetsDevice.asset_id=assetId and
tDevice.id=tAssetsDevice.device_id
and tDevice.latitude!=-1
ORDER BY tDevice.id desc
limit 0,1;
return v_longititue ;
END
}
The final query sql is:
select tAsset.*,fun_getLatitudeByAssetId(tAsset.id) latitude,
fun_getLongititueByAssetId(tAsset.id) longititue from t_asset tAsset
It seems that I have query the latitude and longititue two times,If I want to get the other field from the t_device,I do not want to write another function
like fun_getDeviceCodeByAssetId, How can I optimized my code?

Answer 1

I don't think a function or procedure is the way to go - why not just define a view that has asset_id + all the other fields you want? Then just join to it on asset_id rather than calling functions. In addition to just being cleaner, I'd be concerned about performance with row rather than set processing with the function approach (this is total speculation, I don't have deep enough knowledge of MySQL to know how it's handled)

Answer 2

Is it really necessary to do it with functions?
You can do it with views, for example:
create view latitudeLongitude as
select latitude,longitude,asset_id
from t_device tDevice
inner join t_assets_device tAssetsDevice
on tDevice.id=tAssetsDevice.device_id
and tDevice.latitude!=-1;
Finally your last select should look like this:
select tAsset.*,latitudeLongitude.latitude,
latitudeLongitude.longititue
from t_assettAsset inner join latitudeLongitude
on t_assettAsset.id = latitudeLongitude.asset_id

Answer 3

If you're trying to return several values at once then you should rather declare a stored procedure, not a function. Then you'll be able to write select latitude, longitude from ... inside your procedure and then call it with a command like call getLatAndLong(...)