html - 使用Mysql时如何创建多个组的 View

Question

我正在开展一个项目，需要一份报告。我想依靠这份报告 2014 年 1 月，哪个类(class)的学生进入了 1 月份。学生表只有类(class)号。并且表的表包含了所有的信息。

       Group No 1. month and year.

       Group No 2. Class

       My STD Table


+--------+----------+-----------------+----------------+------------+
| STD_ID | STD_name | Admission_Month | Admission_year | Class_Code |
+--------+----------+-----------------+----------------+------------+
| 01     |  ABC     | January         |  2017          | 1          |
+--------+----------+-----------------+----------------+------------+
| 02     | DEF      | January         |  2017          | 2          |
+--------+----------+-----------------+----------------+------------+
|03      | GHI      | February        |  2017           | 1          |
+--------+----------+-----------------+----------------+------------+

我需要这个输出

+--------+----------+-----------------+----------------+
| Month  | Year     | Class           | Count_Student  |
+--------+----------+-----------------+----------------+
|January | 2017     |     01          |    01          |
+--------+----------+-----------------+----------------+
|January | 2017     |     02          |    01          |
+--------+----------+-----------------+----------------+
|February| 2014     |     01          |    01          | 
+--------+----------+-----------------+----------------+

请大家帮帮我

Answer 1

您可以尝试此解决方案来解决您的问题:

表结构:

CREATE TABLE student ( 
  STD_ID MEDIUMINT NOT NULL AUTO_INCREMENT,
  STd_name varchar(25),
  Admission_Month varchar(25),
  Admission_year varchar(25),
  Class_Code varchar(25),
  std_Status varchar(25),
  PRIMARY KEY (STD_ID) ) #ENGINE=MyISAM;

CREATE TABLE CLASS ( 
  Class_Code MEDIUMINT NOT NULL AUTO_INCREMENT,
  Class_name varchar(25),
  CLass_Courcess varchar(25),
PRIMARY KEY (Class_Code) ) 
#ENGINE=MyISAM;


INSERT INTO student (STd_name, Admission_Month, Admission_year, Class_Code,std_Status)
VALUES ("ABC","January","2017","1","On"),
       ("DEF","January","2017","1","On"),
       ("GHI","February","2017","2","Off"),
       ("ADFDBC","MARCH","2017","1","On");


INSERT INTO CLASS (Class_name,CLass_Courcess)
VALUES("DIV A","MBA"),("DIV B","MTECH")

查询:

    SELECT Admission_Month as Month, Admission_year as Year, Class_name as Class, 
    (SELECT COUNT(s_on.STD_ID) FROM student as s_on WHERE s_on.Admission_Month = student.Admission_Month AND s_on.Admission_year = student.Admission_year AND s_on.Class_Code = student.Class_Code AND s_on.std_Status ="On") as status_on, 
    (SELECT COUNT(s_on.STD_ID) FROM student as s_on WHERE s_on.Admission_Month = student.Admission_Month AND s_on.Admission_year = student.Admission_year AND s_on.Class_Code = student.Class_Code AND s_on.std_Status ="Off") as status_off
    FROM student
    LEFT JOIN class ON class.Class_Code = student.Class_Code
    GROUP BY Admission_Month,Admission_year

您也可以引用sqlfiddle

希望对您有所帮助。