There isn't a built in function like ISNUMERIC, but we can create it.
dbadmin=> create function isnumeric(x varchar) return varchar
dbadmin-> as
dbadmin-> begin
dbadmin-> return REGEXP_COUNT(x, '^[0-9.-]+$');
dbadmin->
dbadmin-> end;
CREATE FUNCTION
dbadmin=> select col1, isnumeric(col1) isnumeric from test;
col1 | isnumeric
------+-----------
100 | 1
25.5 | 1
A | 0
25A | 0
-60 | 1
(5 rows)
