Round ST_Distance

Question

I am looking for a possibillity to round the result of ST_Distance on two digits. If I try

select g.id ,round(ST_Distance(g.geom, p.geom), 2) dist_m

I get:

Funktion round(double precision, integer) existiert nicht

function round(double precision, integer) does not exist

Answer 1

The first place to look is always the PostgreSQL docs (i.e. Mathematical Functions)!

When using the two parameter signature of ROUND(), the function expects a NUMERIC type as its first input; you can simply cast the value (::):

SELECT g.id,
       ROUND(ST_Distance(g.geom, p.geom)::NUMERIC, 2) AS dist_m
FROM   ...
;