\set ECHO none
SELECT format(10000.01, 0);
 format 
--------
 10,000
(1 row)

SELECT format(10000.01, 2);
  format   
-----------
 10,000.01
(1 row)

SELECT format(0.01, 1);
 format 
--------
 0.0
(1 row)

SELECT format(0, 3);
 format 
--------
 0.000
(1 row)

SELECT format(9.95, 1);
 format 
--------
 10.0
(1 row)

SELECT format(9.94999999, 1);
 format 
--------
 9.9
(1 row)

ROLLBACK;