Question

I have this query:

SELECT v2.longitude AS something FROM points AS v2

Now I want to do something like this:

SELECT v2.longitude AS something,2*something FROM points AS v2

but it fails with

points.longitude is a float number

How can I fix this?

EDIT- Here is an example of the current query:

$query="
SELECT 
v2.longitude AS xa,
v2.latitude AS ya,
v3.longitude AS xb,
v3.latitude AS yb, 
(yb-ya)/(xb-xa) AS l,
-1/l AS l_katheto,
(l*xa-l_katheto*$tetmimenh+ya-y1)/(l_katheto-l) AS x_tomh, 
l*(x_tomh-xa)+ya AS y_katheto,
min(
    sqrt(
        (v2.longitude-$tetmimenh)*
        (v2.longitude-$tetmimenh)+
        (v2.latit‌​ude-$tetagmenh)*
        (v2.latitude-$tetagmenh)
    ),
    sqrt(
        (v3.longitude-$tetmimenh)*
        (v3.long‌​itude-$tetmimenh)+
        (v3.latitude-$tetagmenh)*
        (v3.latitude-$tetagmenh)
    ),
    sqrt(
        ($tetmi‌​menh-x_tomh)*
        ($tetmimenh-x_tomh)+
        ($tetagmenh-y_tomh)*
        ($tetagmenh-y_tomh)
    )
) 
FROM 
segments AS v1 
JOIN points AS v2 ON v1.from_point=v2.point_id 
JOIN points AS v3 ON v3.point_id=v1.to_point";

Answer 1

Try this code:

SELECT v2.longitude AS something,2*v2.longitude AS something2 FROM points AS v2