插外键出错

Question

为什么会出现这样的问题呢。新手求帮助，谢谢
SQL> describe Customer;
 Name                                      Null?    Type
 ----------------------------------------- -------- ----------------------------
 CUSTID                                    NOT NULL VARCHAR2(10)
 CUSTNAME                                           VARCHAR2(22)
 CUSTADD                                            VARCHAR2(20)
 CUSTPHONE                                          VARCHAR2(13)
 CUSTFAX                                            VARCHAR2(13)
SQL> describe Ord
 Name                                      Null?    Type
 ----------------------------------------- -------- ----------------------------
 ORDID                                     NOT NULL VARCHAR2(10)
 PROID                                              VARCHAR2(10)
 CUSTID                                             VARCHAR2(10)
 QTY                                                NUMBER(10)
 ORDDATE                                            DATE
 D_DATE                                             DATE
SQL> alter table Ord
  2  add constraint Ord_Custid_fk FOREIGN KEY(CustID) REFERENCES Customer(CustID);
add constraint Ord_Custid_fk FOREIGN KEY(CustID) REFERENCES Customer(CustID)
               *
ERROR at line 2:
ORA-02298: cannot validate (SYSTEM.ORD_CUSTID_FK) - parent keys not found

Answer 1

估计是由于你的Ord表中custid列里有的数据，在父表customer的custid列里找不到。