我每次给它一个null结果时都试图得到'none'的结果。现在它给我一个0表示空结果。我怎么能有一行显示'无'而不是0表示空结果。
我已经尝试了TO_CHAR和TO_NUMBER作为总和而我无法让它显示'无'......
CASE WHEN SUM(ENROLLED) = 0 THEN 'none' ELSE SUM(ENROLLED) END AS ENROLLED
所以在尝试上面的时候我得到SQL错误:ORA-00932:不一致的数据类型:预期的CHAR得到了NUMBER
这就是我所拥有的
SELECT lt.STUDENT_ID,lt.FIRST_NAME, lt.LAST_NAME, CASE WHEN SUM(ENROLLED) = 0 THEN 'none' ELSE SUM(ENROLLED) END AS ENROLLED
FROM STUDENT lt
LEFT OUTER JOIN
(SELECT s.STUDENT_ID, e.ENROLL_DATE,COUNT(z.COURSE_NO)AS ENROLLED
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, e.ENROLL_DATE) 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;
而不是
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
答案 0 :(得分:4)
尝试使用函数:COALESCE(cast(sum(expr1)as varchar),'none')
作为旁注,我质疑在您的查询中使用DISTINCT。
答案 1 :(得分:3)
CASE WHEN SUM(ENROLLED) = 0 THEN 'none' ELSE SUM(ENROLLED) END AS ENROLLED
这会返回不同的类型。使其相同(将SUM转换为字符串)
答案 2 :(得分:1)
错误是正常的,因为您的命令
当SUM(ENROLLED)= 0时的情况那么'没有'和(注册)以注册结束
使用与字符串'none'相同的列和数字SUM(ENROLLED)
您可以将该列用作字符串,并使用
同时显示该数字当SUM(ENROLLED)= 0时,'无'ELSE TO_CHAR (SUM(ENROLLED))END IN ENROLLED
答案 3 :(得分:0)
试试这个:
COALESCE(to_char(sum(expr1)), 'none')
这应该不使用cast和varchar。