Question

现在，当我计算注册日期时，我的查询给了我一个0。我怎么能有一行显示'无'结果而不是0。

我在这里缺少什么？

COALESCE(TO_CHAR(SUM(ENROLLMENTS)),'none') ENROLLMENTS

这就是我所拥有的

SELECT lt.STUDENT_ID,lt.FIRST_NAME, lt.LAST_NAME,COALESCE(TO_CHAR(SUM(ENROLLMENTS)),'none') ENROLLMENTS
FROM STUDENT lt
LEFT OUTER JOIN
(SELECT s.STUDENT_ID, z.COURSE_NO,COUNT(e.ENROLL_DATE) AS ENROLLMENTS
FROM   STUDENT s
LEFT   JOIN ENROLLMENT e ON s.STUDENT_ID = e.STUDENT_ID
LEFT   JOIN SECTION z ON e.SECTION_ID = z.SECTION_ID
WHERE  s.PHONE LIKE '702%'
GROUP  BY s.STUDENT_ID, z.COURSE_NO) rt
ON lt.STUDENT_ID = rt.STUDENT_ID
WHERE lt.PHONE LIKE '702%'
GROUP BY lt.STUDENT_ID,lt.FIRST_NAME, lt.LAST_NAME,ENROLLMENTS
ORDER BY lt.LAST_NAME,lt.FIRST_NAME;

而不是结果

STUDENT_ID FIRST_NAME                LAST_NAME                 ENROLLED
---------- ------------------------- ------------------------- -----------
       253 Walter                    Boremmann                     1 
       396 James E.                  Norman                        0 
etc

我想要像这样

STUDENT_ID FIRST_NAME                LAST_NAME                 ENROLLED
---------- ------------------------- ------------------------- -----------
       253 Walter                    Boremmann                     1 
       396 James E.                  Norman                        none
etc

Answer 1

我认为您需要CASE声明，因为TO_CHAR正在返回"0"：

(CASE WHEN SUM(ENROLLMENTS)=0 THEN 'none' ELSE SUM(ENROLLMENTS) END) ENROLLMENTS

不显示'none'而不是0

1 个答案: