SQL> describe student;

Name Type Nullable Default Comments

------------ ------------ -------- ------- --------

ID NUMBER(10)

TEACHER_ID NUMBER(10) Y

STUDENT_NAME VARCHAR2(20) Y '嗯嗯嗯'

SAL NUMBER(20) Y

SEX VARCHAR2(2) Y

SQL> describe teacher;

Name Type Nullable Default Comments

------------ ------------ -------- ------- --------

ID NUMBER(10) Y

TEACHER_NAME VARCHAR2(20) Y

查看兩個表約束基本信息

SQL> select table_name,constraint_name,constraint_type,status from user_constraints where table_name='TEACHER';

TABLE_NAME CONSTRAINT_NAME CONSTRAINT_TYPE STATUS

------------------------------ ------------------------------ --------------- --------

TEACHER TEACHER2 P DISABLED

TEACHER TEACHER C ENABLED

TEACHER UQ_NAME U ENABLED

SQL> select table_name,constraint_name,constraint_type,status from user_constraints where table_name='STUDENT';

TABLE_NAME CONSTRAINT_NAME CONSTRAINT_TYPE STATUS

------------------------------ ------------------------------ --------------- --------

STUDENT CHK_STUDENT C ENABLED

STUDENT PK_STUDENT P ENABLED

查看約束建立那些列結構

SQL> select table_name,constraint_name,column_name from user_cons_columns where table_name='TEACHER';

TABLE_NAME CONSTRAINT_NAME COLUMN_NAME

------------------------------ ------------------------------ ------------------------------------------------

TEACHER UQ_NAME TEACHER_NAME

TEACHER TEACHER2 ID

TEACHER TEACHER ID

SQL> select table_name,constraint_name,column_name from user_cons_columns where table_name='STUDENT';

TABLE_NAME CONSTRAINT_NAME COLUMN_NAME

------------------------------ ------------------------------ ------------------------------------------------

STUDENT PK_STUDENT ID

STUDENT CHK_STUDENT SAL

STUDENT CHK_STUDENT SEX

關聯兩個表的id號的時候報錯

SQL> alter table student add constraint fk_student foreign key (TEACHER_ID) references teacher (ID);

alter table student add constraint fk_student foreign key (TEACHER_ID) references teacher (ID)

ORA-02270: 此列列表的唯一關鍵字或主鍵不匹配

解決思路

1、查看綁定主鍵與外鍵數據類型不同（數據是否相同）

2、查看主鍵是否還有其他約束（外鍵貌似只能綁定主鍵），是否還有其他的檢測約束等等

3、認真觀察仔細，鍵值的狀態是否開啟！

本題總結

因為第一張表主鍵約束被關閉，所以導致外鍵正常連接，小錯誤決成敗。

解決步驟

SQL> alter table teacher modify constraint TEACHER2 ENABLE;

Table altered

SQL> alter table student add constraint fk_student foreign key (TEACHER_ID) references teacher (ID);

Table altered

關聯成功！

ORA-02270: 此列列表的唯一關鍵字或主鍵不匹配一些思路