我想显示教师的全名和他们目前正在教授的类(class)数量。
我的查询是:
SELECT CONCAT( FName, ' ', LName ) AS "Faculty Names", course.CourseName AS 'NUmbers Of Courses'
FROM Faculty LEFT JOIN course ON (course.FacultyID = faculty.FacultyID)
ORDER BY faculty.FacultyID`
问题 1:我想在“类(class)数量”列中计算类(class)名称(4,2,5),但显示的输出是完整的类(class)名称。
问题 2:在“类(class)编号”列中使用左联接,一些行具有 Null 值,但我想在那里显示 0。
最佳答案
您需要一个GROUP BY
和COUNT
。检查这个 -
SELECT CONCAT( FName, ' ', LName ) AS "Faculty Names",
COUNT(course.CourseName) AS 'NUmbers Of Courses', faculty.FacultyID
FROM Faculty
LEFT JOIN course ON (course.FacultyID = faculty.FacultyID)
GROUP BY faculty.FacultyID, "Faculty Names"
ORDER BY faculty.FacultyID
Note : You should include FacultyID while
GROUP BY
, because, you never can be sure that you will not have sameFName
+LName
for any 2 Facultes.
关于mysql - 我想在 "Numbers Of Courses"列中计算 CourseName like(4,2,5),但输出显示的是完整的 courseName,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/34230406/