postgres=#
postgres=# -- trunc(x): Returns the value of x, with any digits past the decimal point truncated
postgres=# -- trunc(x, s): Returns the value of x, with any digits past s decimal points truncated
postgres=# SELECT trunc(1.598) AS natural_truncation,
postgres-# trunc(1.598, 1) AS one_decimal_point,
postgres-# trunc(1.598, 8) AS extra_places;
natural_truncation | one_decimal_point | extra_places
--------------------+-------------------+--------------
1 | 1.5 | 1.59800000
(1 row)
postgres=#