SQL查询，用于在一周中的每一天为项目排序的EACH类别中查找UNITS

Question

下面是我需要的详细信息：

1. EACH类别的查找单位，在过去7天的每周的每一天都已订购。-输出为：

Category | Sunday_units | Monday_units | Tuesday_units | Wednesday_units | Thursday_units | Friday_units | Saturday_units

2. 为每位客户至少下达两个订单的日期查找第二个最早的ORDER_ID

   我也想用这些表的映射来开发ER模型。为了开发具有基数的ER模型，我认为：1个项目->可以有1个或多个订单1个订单--->只能有一个物料（根据架构）请验证模型基数是否正确。

我尝试使用case语句查找SQL Server查询。

模式：

ORDERS

order_id varchar(20) composite primary key
customer_id numeric(35,0)
order_datetime timestamp
item_id varchar(10) composite primary key
order_quantity numeric(35,0)

从ORDERS中提取的样本

order_id | customer_id | order_datetime | item_id | order_quantity
A-001    | 32483       | 2018-12-15 09:15:22 | B000 | 3                 
A-005    | 21456       | 2019-01-12 09:28:35 | B001 | 1
A-005    | 21456       | 2019-01-12 09:28:35 | B005 | 1
A-006    | 42491       | 2019-01-16 02:52:07 | B008 | 2

ITEMS

item_id varchar(10) primary key
item_category varchar(18)

从ITEMS中提取的样本

item_id | item_category
B000 | Outdoors
B001 | Outdoors
B002 | Outdoors
B003 | Kitchen
B004 | Kitchen

我创建的查询如下：

查看查询，我们如何知道2019年10月10日是星期四？我还想知道日期和相应的星期计算。

Select i.item_category, 
     Sum(case when o.order_datetime = '01-10-2019' THEN o.Count(order_quantity) else null end) as Thursday_Units,
     Sum(case when o.order_datetime = '01-11-2019' THEN o.Count(order_quantity) else null end) as Friday_Units,
     Sum(case when o.order_datetime = '01-12-2019' THEN o.Count(order_quantity) else null end) as Saturday_Units,
     Sum(case when o.order_datetime = '01-13-2019' THEN o.Count(order_quantity) else null end) as Sunday_Units,
     Sum(case when o.order_datetime = '01-14-2019' THEN o.Count(order_quantity) else null end) as Monday_Units,
     Sum(case when o.order_datetime = '01-15-2019' THEN o.Count(order_quantity) else null end) as Tuesday_Units,
     Sum(case when o.order_datetime = '01-16-2019' THEN o.Count(order_quantity) else null end) as Wednesday_Units
     from Orders o inner join Items i
     on o.item_id = i.item_id
     group by i.item_category

Answer 1

您可以使用datename()：

select 
    i.item_category, 
    sum(case when datename(weekday, o.order_datetime) = 'Sunday' then order_quantity end) as sunday_units,
    sum(case when datename(weekday, o.order_datetime) = 'Monday' then order_quantity end) as monday_units,
    ...
    sum(case when datename(weekday, o.order_datetime) = 'Saturday' then order_quantity end) as saturday_units,
from orders o 
inner join items i  on o.item_id = i.item_id
where o.order_datetime >= dateadd(day, -7, cast(getdate() as date))
group by i.item_category