sql - Conditional Value -

i have table uses uuids primary keys. new rows inserted this

insert ( id, ... ) values ( uuid_generate_v4(), ...) 

now want generate uuid when no id provided in insert (either null or empty string)

is possible write this?

insert ( id, ... ) values ( $1 || uuid_generate_v4(), ...) 

the coalesce() function use first non-null. if $1 null, coalesce() use uuid_generate_v4(). otherwise, try use $1.

insert (id, ... ) values  (coalesce($1, uuid_generate_v4()), ... );