MySQL
CREATE USER 'readonly_user'@'%' IDENTIFIED BY 'your_password';
GRANT SELECT ON your_database.* TO 'readonly_user'@'%';
FLUSH PRIVILEGES;
PostgreSQL
CREATE ROLE readonly_user WITH LOGIN PASSWORD 'your_password';
GRANT CONNECT ON DATABASE your_database TO readonly_user;
GRANT USAGE ON SCHEMA public TO readonly_user;
GRANT SELECT ON ALL TABLES IN SCHEMA public TO readonly_user;
ALTER DEFAULT PRIVILEGES IN SCHEMA public
GRANT SELECT ON TABLES TO readonly_user;
