Question

我试图获得每年/每月的出勤率类型以填充条形图。这是我的两张桌子（我知道英语有点偏差）：

import java.util.ArrayList;
import main.ClassPessoa;
import main.ClassCliente;
import main.ClassFornecedor;
import main.ClassStock;
import main.ClassVenda;
import main.ClassRecurso;
import java.io.Serializable;

/**
*
* @author Skray
*/
public class ClassListas implements Serializable {
    //Listas
    public static ArrayList<ClassPessoa> ListaPessoa = new ArrayList<ClassPessoa>();
    public static ArrayList<ClassCliente> ListaCliente = new ArrayList<ClassCliente>();
    public static ArrayList<ClassFornecedor> ListaFornecedor = new ArrayList<ClassFornecedor>();
    public static ArrayList<ClassStock> ListaStocks = new ArrayList<ClassStock>();
    public static ArrayList<ClassVenda> ListaVenda = new ArrayList<ClassVenda>();
    public static ArrayList<ClassRecurso> ListaRecurso = new ArrayList<ClassRecurso>();
}

这是我当前的查询，它返回所有结果而不是预期结果，这只是当前年份：

**presences**
ID | Id_student | Id_class | Presence
3        2           27         1
4        4           28         2
...     ...         ...        ...

**class**
ID | Id_schedule | Date_class | State
27        6        2017-12-11     1
28        7        2018-01-13     1
...      ...          ...        ...

这是结果，也显示了去年的事件：

   SELECT
        DATE_FORMAT(Date_class, '%Y') as 'year', DATE_FORMAT(Date_class, '%M') as 'month',
        (SELECT COUNT(distinct ID) FROM presences WHERE Presence = 0) as Faltas,
        (SELECT COUNT(distinct ID) FROM presences WHERE Presence = 1) as Pre,
        (SELECT COUNT(distinct ID) FROM presences WHERE Presence = 2) as Temp,
        (SELECT COUNT(distinct ID) FROM presences WHERE Presence = 3) as Canc,
        (SELECT COUNT(distinct ID) FROM presences WHERE Presence = 4) as FaltasTemp
    FROM class, presences
    WHERE YEAR(Date_class) = YEAR(CURDATE())
    AND
    presences.Id_class = class.ID
    GROUP BY DATE_FORMAT(Date_class, '%Y%m')

有人能帮我辨别失踪的东西吗？

Answer 1

我认为你想要一个更简单的查询：

   SELECT YEAR(c.Date_class) as year, MONTH(c.Date_class) as month,
          SUM(p.Presence = 0) as Faltas,
          SUM(p.Presence = 1) as Pre,
          SUM(p.Presence = 2) as Temp,
          SUM(p.Presence = 3) as Canc,
          SUM(p.Presence = 4) as FaltasTemp
    FROM class c JOIN
         presences p
         ON p.Id_class = c.ID
    WHERE YEAR(c.Date_class) = YEAR(CURDATE())
    GROUP BY YEAR(c.Date_class), MONTH(c.Date_class);

注意：

使用正确的，明确的JOIN语法。从不在FROM子句中使用逗号。
这些表有别名，这使得查询更容易编写和阅读。
这些列都是合格的（使用表名），因此您可以知道它们的来源。
您不需要为每列提供单独的子查询。

按月分组计数结果

1 个答案: