查询mysql所有外键约束

SELECT C.TABLE_SCHEMA            拥有者,
           C.REFERENCED_TABLE_NAME  父表名称 ,
           C.REFERENCED_COLUMN_NAME 父表字段 ,
           C.TABLE_NAME             子表名称,
           C.COLUMN_NAME            子表字段,
           C.CONSTRAINT_NAME        约束名,
           T.TABLE_COMMENT          表注释,
           R.UPDATE_RULE            约束更新规则,
           R.DELETE_RULE            约束删除规则
      FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE C
      JOIN INFORMATION_SCHEMA. TABLES T
        ON T.TABLE_NAME = C.TABLE_NAME
      JOIN INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS R
        ON R.TABLE_NAME = C.TABLE_NAME
       AND R.CONSTRAINT_NAME = C.CONSTRAINT_NAME
       AND R.REFERENCED_TABLE_NAME = C.REFERENCED_TABLE_NAME
      WHERE C.REFERENCED_TABLE_NAME IS NOT NULL ; 

结果：

外键约束创建的SQL：

ALTER TABLE course ADD CONSTRAINT FK_course_teacher FOREIGN KEY(Tid) REFERENCES teacher(Tid);
ALTER TABLE sc ADD CONSTRAINT FK_sc_student FOREIGN KEY(S) REFERENCES student(S);
ALTER TABLE sc ADD CONSTRAINT FK_sc_course FOREIGN KEY(C) REFERENCES course(Cid);

外键约束删除的SQL：

ALTER TABLE course DROP FOREIGN KEY Tid

附：添加唯一联合索引：

ALTER TABLE sc ADD UNIQUE INDEX idx_s_c(s,c)