Question

我正在尝试进行更新，但似乎一直在遇到这个特定的错误代码。当我运行在外部WHERE子句中找到的嵌套SELECT语句时，我能够提取需要更新的正确条目，但是一旦我尝试运行应该提交更改的完整语句，我就会遇到错误。

UPDATE expertise
SET expertise_level = (expertise_level + 1)
WHERE expertise_level = (SELECT UNIQUE expertise_level, cs.instructor_id
    FROM class_section cs JOIN course c ON (cs.course_code = c.course_code)
    JOIN expertise e ON (c.course_code = e.course_code)
    WHERE (expertise_level < 10) AND (year = '2016'));

我的语法中是否缺少某些内容，或者可能是构建查询的更好方法？谢谢！

Answer 1

看看你的陈述......

...
WHERE expertise_level = (SELECT UNIQUE expertise_level, cs.instructor_id
    FROM class_section 
...

怎么可以＆＃34; expertise_level＆＃34;等于＆＃34; expertise_level，instructor_id＆＃34; ？

Answer 2

您的子查询有两列，但只与一个列进行比较。执行所需操作的一种方法是使用相关子查询：

UPDATE expertise
    SET expertise_level = expertise_level + 1
    WHERE expertise_level = (SELECT expertise_level
                             FROM class_section cs JOIN
                                  course c
                                  ON cs.course_code = c.course_code 
                             WHERE c.course_code = e.course_code AND
                                   expertise_level < 10 AND 
                                   year = '2016'
                            );

如果可以有多个匹配项，您可能需要使用IN。

另一个选项使用=或IN使用元组：

UPDATE expertise
    SET expertise_level = expertise_level + 1
    WHERE (course_code, expertise_level) =
              (SELECT c.course_code, expertise_level
               FROM class_section cs JOIN
                    course c
                    ON cs.course_code = c.course_code 
               WHERE expertise_level < 10 AND 
                     year = '2016'
              );

目前还不清楚教练是否应该包含在你的逻辑中;它似乎是语法错误的原因。

ORA-00913：价值太多了

2 个答案: