MySQL：计算一个新列（将天转换为周）以获取产品的每周销售额答案

【问题标题】：MySQL: Calculate a new column (converting days to week) to get weekly sales of productsMySQL：计算一个新列（将天转换为周）以获取产品的每周销售额
【发布时间】：2017-05-02 12:04:32
【问题描述】：

我在mysql中的表sales是这样的：

ID             Date     Quantity
00000001    01/01/2017  5
00000002    02/01/2017  25
00000003    01/01/2017  2
00000001    04/01/2017  58
00000005    01/01/2017  8
00000001    10/01/2017  2

我想获得每种产品的每周销售额（在本例中为第 1 周）。以下是我的查询

SELECT ID, 
    IF (YEARWEEK(Date) = '201401', SUM(Quantity), NULL) AS WEEK1
FROM sales
GROUP BY ID

它返回以下错误：

#1055 - Expression #2 of SELECT list is not in GROUP BY clause and contains nonaggregated column 'sales.registerDate' which is not functionally dependent on columns in GROUP BY clause; this is incompatible with sql_mode=only_full_group_by

我也使用过 CASE 语句，但它对我来说不能正常工作。

SELECT ID, 
    CASE WHEN  (YEARWEEK(Date) = '201401' THEN SUM(Quantity) END AS WEEK1
FROM sales
GROUP BY ID

返回错误

#1064 - You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'THEN SUM(Quantity) END) WEEK1
FROM sales
GROUP BY ID' at line 2

预期的结果格式是

   ID     week1
00000001    63
00000002    25
00000003    2
00000005    8

获得预期结果的正确方法是什么？

【问题讨论】：

在第一个SELECT 中您是否尝试在GROUP BY 中添加YEARWEEK(registerDate)？

标签： mysql datetime group-by case

【解决方案1】：

尝试总结 case 语句，例如：

SELECT ID, 
    SUM(CASE WHEN YEARWEEK(Date) = '201401' THEN Quantity END) AS WEEK1
FROM sales
GROUP BY ID

【讨论】：

【解决方案2】：

我会取出 case 语句，因为它似乎不需要，您只是使用它来选择 YEARWEEK 是“201401”的位置。一个更简单的查询可能是：

SELECT
    ID
    , SUM(QUANTITY)
    , YEARWEEK(DATE) AS YEAR_WEEK
FROM 
    SALES 
WHERE 
    YEAR_WEEK = '201401'
GROUP BY
    ID
    , YEAR_WEEK

【讨论】：