変更テーブルの削除時のSQLトリガー

トリガーでPRAGMAAUTONOMOUS_TRANSACTIONを使用してみてください。

Oracleドキュメント： https://docs.oracle.com/ cd / B14117_01 / appdev.101 / b10807 / 13_elems002.htm

    CREATE OR REPLACE TRIGGER planes_del_trigg
            BEFORE DELETE ON planes
        DECLARE 
            CURSOR dist_cur IS
                SELECT distance
                FROM flights;
            v_dist flights.distance%TYPE;
            v_counter NUMBER(3);

 PRAGMA AUTONOMOUS_TRANSACTION;
        BEGIN
            OPEN dist_cur;
            LOOP
                FETCH dist_cur INTO v_dist;
                IF v_dist <= :OLD.range THEN
                    v_counter := v_counter + 1;
                END IF;
                EXIT WHEN dist_cur%NOTFOUND;
            END LOOP;
            CLOSE dist_cur;
            IF v_counter >= 3 THEN
                RAISE_APPLICATION_ERROR(-20501, 'This plane cannot be deleted!');
            END IF;
        END planes_del_trigg;