Question

我正在尝试根据本教程Using MySQL to generate daily sales reports with filled gaps为特定用户生成每日销售报告。为此，我有三个表，记录表，用户表和日历表

records     user      calendar
id          id        datefield
user_id     
timestamp

下面的查询返回0作为total，并且当数据在特定日期不可用时，返回NULL作为user_id：

SELECT calendar.datefield AS DATE,
       IFNULL(COUNT(records.id),0) AS total, records.user_id
FROM records 
RIGHT JOIN calendar ON (DATE(records.timestamp) = calendar.datefield)    

WHERE ( 
    calendar.datefield BETWEEN (NOW() - INTERVAL 14 DAY) AND NOW()
)
GROUP BY DATE DESC

我们的想法是为特定用户生成此报告，因此我将上述查询修改为以下内容：

SELECT calendar.datefield AS DATE,
           IFNULL(COUNT(records.id),0) AS total, records.user_id
    FROM records 
    RIGHT JOIN calendar ON (DATE(records.timestamp) = calendar.datefield)

    WHERE ( 
        calendar.datefield BETWEEN (NOW() - INTERVAL 14 DAY) AND NOW()
        AND records.user_id = SOME_EXISTING_USER_ID
    )
    GROUP BY DATE DESC

当没有记录时返回空结果，但想法是在没有数据的任何特定日期返回0。

如何修改第一个查询以适合特定用户？

Answer 1

哇。自从我在野外见过RIGHT JOIN以来已经有一段时间了！无论如何，尝试将WHERE子句中的用户谓词添加到RIGHT JOIN中，如下所示：

SELECT calendar.datefield AS DATE,
           IFNULL(COUNT(records.id),0) AS total, records.user_id
    FROM records 
    RIGHT JOIN calendar ON (DATE(records.timestamp) = calendar.datefield) 
                        AND records.user_id = SOME_EXISTING_USER_ID

    WHERE ( 
        calendar.datefield BETWEEN (NOW() - INTERVAL 14 DAY) AND NOW()
    )
    GROUP BY DATE DESC;

对我而言，这是显式连接与隐式连接的巨大好处之一......

每天分组填补空白

1 个答案: