SQL中的日期时间戳查询

Question

我是一个 SQL 初学者并且有一个查询以查找在 2015 年 5 月预订最后一次销售的人的 ID， occurred_at的列是datetime时间（2015-10-06 17:31:14），我不知道如何从中获得 2015 年 5 月预订的最后一笔销售。

这是我在下面的查询，它说没有作为Sales_Date的列。 请帮忙

SELECT 
    ID, 
    CAST(occurred_at AS time) AS sales_time,
    CONCAT(' ', CAST(occurred_at AS DATE)) AS Sales_Date,
    extract(year from sales_date) AS year, 
    extract(month from sales_date) AS Month  
FROM
    <table name >
WHERE 
    year = 2015 AND month = 05 
ORDER BY 
    sales_time DESC

Answer 1

如果您想获得最后一次销售，为什么不直接使用 MAX(occured_at) 和 year = 2015？

Answer 2

您还需要在where子句中提取年份和月份。

SELECT ID , CAST(occurred_at AS time ) AS sales_time  ,
       CONCAT ( ' ' , CAST(occurred_at AS DATE) ) AS Sales_Date ,
       extract ( year from sales_date) AS year , 
       extract ( month from sales_date) AS Month  
from <table name >
where extract(year from sales_date) = 2015 and extract(month from sales_date) = 5 
order by sales_time desc