Postgresql varchar to int -

i have clothes size column in postgresql containing values such (24, 25, "s", "m", "onesize", "xl").

i need extract integer values , convert result int. tried to_number in format below, works if row contains number, not work if contains letters.

select to_number('aq1', '99999d9') -> 1 select to_number('23', '99999d9') -> 23 select to_number('onesize', '99999d9') -> error 

i need function work in way allow me join on varchar column equal int column.

select ???func("xl") -> null/0 select ???func(23) -> 23 

any appreciated

try one:

select coalesce((select unnest(regexp_matches('xlds', '\d+')::integer[])), 0); 

notice regexp matches first number in string.