错误报告 - ORA-25155：NATURAL 连接中使用的列不能有限定符 25155。00000 - “NATURAL 连接中使用的列不能有限定符”

当我运行此行时，它给出了以下错误。

CREATE VIEW student_view AS 
SELECT Student.*, Course.*, Grade.* 
FROM (Student 
      NATURAL LEFT OUTER JOIN Grade 
      NATURAL LEFT OUTER JOIN Course)
UNION ALL
SELECT Student.*, Course.*, Grade.* 
FROM (Course 
      NATURAL LEFT OUTER JOIN Grade 
      NATURAL LEFT OUTER JOIN Student)
WHERE Student.StudentID is NULL

*原因：用于命名连接的列（自然连接 或带有 USING 子句的连接）不能有显式限定符。

*操作：删除限定符

正如其他人所提到的，自然连接一直是一个坏主意。如果有人添加一个怎么办description列到两者COURSE and GRADE？无论如何，自然连接中使用的列不能用表别名限定。

create table student
( student_id integer primary key
, student_name varchar2(30) not null );

create table course
( course_id integer primary key
, course_name varchar2(30) not null );

create table grade
( student_id references student not null
, course_id  references course not null
, grade varchar2(3) not null );

Query:

select student_id, student_name, course_id, course_name, grade
from   student 
       natural left join grade 
       natural left join course;

创建视图：

create or replace view student_view as 
select course_id, student_id, student_name, grade, course_name
from   student 
       natural left outer join grade 
       natural left outer join course
union all
select course_id, student_id, student_name, grade, course_name
from   course 
       natural left outer join grade 
       natural left outer join student
where  student_id is null;

继续您的其他问题... https://stackoverflow.com/a/63203808/230471