Question

我想问一下我的sql从视图中找到最大值和最小值。

我创建了一个视图：

create VIEW Count_Of_Appointment AS
SELECT ap.doctorID, COUNT(*) AS NumberOfAppointment, CONCAT(d.surname,'', d.given) AS doctor_name
FROM appointment AS ap Inner join doctor AS d
    ON ap.doctorid = d.doctorID
GROUP BY doctorID
ORDER BY COUNT(*)

现在，我想找到使用该视图的医生的min +名称。

这是我的代码：

SELECT a2.*
FROM
    (
    SELECT ap.doctorID, COUNT(*) AS Number, CONCAT(d.surname,'', d.given) AS doctor_name
    FROM appointment AS ap Inner join doctor AS d
        ON ap.doctorid = d.doctorID
    GROUP BY doctorID
    ORDER BY COUNT(*)
    )a2
INNER JOIN 
(
SELECT MIN(Number) AS NumberOfAppointment 
FROM
    (
    SELECT ap.doctorID, COUNT(*) AS Number, CONCAT(d.surname,'', d.given) AS doctor_name
    FROM appointment AS ap Inner join doctor AS d
        ON ap.doctorid = d.doctorID
    GROUP BY doctorID
    ORDER BY COUNT(*)
    )a1
)b 
ON a2.Number = b.NumberOfAppointment

我在使用视图之前正在执行该代码。如何使用FROM VIEW Count_Of_Appointment转换它们？

Answer 1

以下是如何使用MySQL获取最小和最大聚合函数

SELECT student_name, MIN(test_score), MAX(test_score)
    FROM student
    GROUP BY student_name;

如果你想把它作为一个视图

CREATE VIEW vw_student_score AS 
   SELECT student_name, MIN(test_score), MAX(test_score)
    FROM student
    GROUP BY student_name;

从视图中搜索最大值和最小值

1 个答案: