格式輸出，B列的多個值與列的一個值相關聯的

Question

這是我的select語句：

SELECT lastName + ',' + firstName as Name, 
     classNumber 
FROM STUDENT 
RIGHT JOIN ENROLL ON Enroll.stuid = Student.stuid 

和輸出：

name   classnumber 
-------------------------- 
Smith,Tom  ART103A 
Smith,Tom  HST205A 
Chin,Ann  ART103A 
Chin,Ann  CSC201A 
Chin,Ann  MTH103A 
McCarthy,Owen ART103A 
McCarthy,Owen MTH103C 
Rivera,Jane CSC201A 
Rivera,Jane MTH101B 

我想它以便每個名稱只出現在第一列一次。任何幫助或想法非常感謝。

Answer 1

由於行是彼此獨立的，所以沒有行可以知道它是否是第一個行。

你可以做的就是GROUP BY名稱並把所有的classNumbers在一起，像這樣的列表：

SELECT lastName + ',' + firstName AS Name, 
     GROUP_CONCAT(classNumber SEPARATOR '\n') AS classNumbers 
FROM student 
RIGHT JOIN Enroll ON (Student.stuid = Enroll.stuid) 
GROUP BY Name 

Answer 2

如果只有一個類將出現。

SELECT lastName + ',' + firstName as Name, classNumber 
FROM STUDENT 
RIGHT JOIN 
(select Student.stuid as stuid, min(classNumber) as ClassNumber 
from ENROLL Enroll inner Join Student 
ON (Student.stuid = Enroll.stuid) group by Student.stuid) AS NewEnrol 
ON NewEnroll.stuid = Student.stuid 

或者

SELECT lastName + ',' + firstName as Name,Min(classNumber) 
FROM STUDENT 
RIGHT JOIN ENROLL ON Enroll.stuid = Student.stuid 
Group By lastname+','+firstname