ORA-02270: 此列列表的唯一关键字或主键不匹配一些思路

查看两个表的结构
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

查看两个表约束基本信息
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

查看约束建立那些列结构
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

关联两个表的id号的时候报错（外键关联主键）
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: 此列列表的唯一关键字或主键不匹配

解决思路
1、查看绑定主键与外键数据类型不同（数据是否相同）
2、查看主键是否还有其他约束（外键貌似只能绑定主键），是否还有其他的检测约束等等
3、认真观察仔细，键值的状态是否开启！
本题总结
因为第一张表主键约束被关闭（约束状态红色标记），所以导致外键正常连接，小错误决成败。
解决步骤
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
关联成功！