I have table users with json column details.
I want to fetch all user records where details[\"email\"] is null or email key doesn\'t exist.
use brackets (). Looks like compiler tries to see it like details->('email' IS NOT NULL). So you can fix it like this:
select *
from users
where (details->'email') is not null
sql fiddle demo
actually, to get records where details["email"] is null or email key doesn't exist, you can use this query:
select *
from users
where (details->>'email') is null
as described in this answer.