create table list_changes (
    cind_operation varchar(100),
    change_time TIMESTAMP
);

CREATE OR REPLACE FUNCTION process_check_changes() RETURNS TRIGGER AS $new_emp$
    BEGIN
        if(TG_OP = 'UPDATE') THEN
            INSERT INTO list_chahges(cind_operation, change_time) VALUES('update row', NOW());
        ELSIF (TG_OP = 'DELETE') THEN
            INSERT INTO list_chahges(cind_operation, change_time) VALUES('delete row', NOW());
        ELSIF (TG_OP = 'INSERT') THEN
            INSERT INTO list_chahges(cind_operation, change_time) VALUES('add new row', NOW());
        END IF;
        RETURN NULL;
    END;
$new_emp$ LANGUAGE plpgsql;

CREATE TRIGGER update_list_changes
AFTER INSERT OR UPDATE OR DELETE ON sheldule
    FOR EACH ROW EXECUTE FUNCTION process_check_changes();