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" [英] Error report - ORA-25155: column used in NATURAL join cannot have qualifier 25155. 00000 - "column used in NATURAL join cannot have qualifier"

问题描述

当我运行这条线时，它给了我下面的错误.

CREATE VIEW student_view ASSELECT Student.*, Course.*, Grade.*发件人(学生自然左外连接等级自然左外连接课程)联合所有SELECT Student.*, Course.*, Grade.*从(当然自然左外连接等级自然左外连接学生)WHERE Student.StudentID 为 NULL

<块引用>

*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

解决方案

正如其他人提到的，自然连接一直是个坏主意.如果有人将 description 列添加到 COURSE 和 GRADE 会怎样?无论如何，自然连接中使用的列不能用表别名进行限定.

创建表student( student_id 整数主键, student_name varchar2(30) not null );创建表课程( course_id 整数主键, course_name varchar2(30) not null );创建表等级( student_id 引用 student 不为空, course_id 引用 course not null, 等级 varchar2(3) 不为 null );

查询:

选择student_id、student_name、course_id、course_name、成绩来自学生自然左连接等级自然左连接课程；

创建视图:

创建或替换视图 student_view 为选择 course_id、student_id、student_name、成绩、course_name来自学生自然左外连接等级自然左外连接课程联合所有选择 course_id、student_id、student_name、成绩、course_name从课程自然左外连接等级自然左外加入学生其中 student_id 为空；

继续您的其他问题...

When I am running this lines, it is giving me the error below.

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

*Cause: Columns that are used for a named-join (either a NATURAL join or a join with a USING clause) cannot have an explicit qualifier.

*Action: Remove the qualifier

解决方案

As others have mentioned, natural joins have always been a bad idea. What if someone adds a description column to both COURSE and GRADE? Anyway, columns used in a natural join can't be qualified with a table alias.

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;

Create a view:

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;

Continued on your other question...

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