SQL DOESNT ALLOWE ME TO INSERT DATA : 

    creating table and inserting data into a table and now it giving me an error  SQL Error: ORA-02291: integrity constraint (S21403051.SYS_C007300) violated - parent key not found         02291. 00000 - "integrity constraint (%s.%s) violated - parent key not found"         *Cause:   

    CREATE TABLE CUSTOMER(
     CUSTOMER_ID VARCHAR(10) PRIMARY KEY,
     FIRST_NAME  VARCHAR(10),
     SURNAME VARCHAR(15),
     CUSTOMER_TEL VARCHAR(12),
    CUSTOMER_EMAIL VARCHAR(30)
    )
    
    INSERT INTO CUSTOMER_CRUISES VALUES ( 'CRUISE_1', 'CUST_102', 'EMP_51');
    INSERT INTO CUSTOMER_CRUISES VALUES ( 'CRUISE_3','CUST_101','EMP_51');
    INSERT INTO CUSTOMER_CRUISES VALUES ( 'CRUISE_3','CUST_101','EMP_53');
    INSERT INTO CUSTOMER_CRUISES VALUES ( 'CRUISE_5','CUST_103','EMP_54');
    INSERT INTO CUSTOMER_CRUISES VALUES ( 'CRUISE_5','CUST_107','EMP_54');
    INSERT INTO CUSTOMER_CRUISES VALUES ( 'CRUISE_1', 'CUST_106','EMP_55');
    INSERT INTO CUSTOMER_CRUISES VALUES ( 'CRUISE_1','CUST_108','EMP_55');
    INSERT INTO CUSTOMER_CRUISES VALUES ( 'CRUISE_5','CUST_104','EMP_51');
    INSERT INTO CUSTOMER_CRUISES VALUES ( 'CRUISE_3','CUST_109','EMP_51');
    INSERT INTO CUSTOMER_CRUISES VALUES ( 'CRUISE_2','CUST_1010','EMP_52');
    INSERT INTO CUSTOMER_CRUISES VALUES ( 'CRUISE_2','CUST_1010','EMP_55');
    INSERT INTO CUSTOMER_CRUISES VALUES ( 'CRUISE_5','CUST_101','EMP_51');
    INSERT INTO CUSTOMER_CRUISES VALUES ( 'CRUISE_5','CUST_103','EMP_51');


IT GIVE ME ERROR SQL Error: ORA-02291: integrity constraint (S21403051.SYS_C007300) violated - parent key not found         02291. 00000 - "integrity constraint (%s.%s) violated - parent key not found"         *Cause:  
