试图获得一个 SQL 命令来获取每个月的新客户，但我似乎无法让它工作

Question

我正在尝试从 SQL 数据库中提取每个月的新客户。我试过这个：

SELECT COUNT (Name) 
FROM Customer 
WHERE Date_created BETWEEN CONVERT(date, getdate()) AND CONVERT(date, getdate()) - (30)

Answer 1

您可以使用 convert(varchar(6), getdate(), 112) 获取 yyyymm 格式的月份：

SELECT  convert(varchar(6), getdate(), 112) as Month
,       count(*)
FROM    Customer
GROUP BY
        convert(varchar(6), getdate(), 112)

Answer 2

标准 SQL:

select
   extract(year from Date_created) as yr
  ,extract(month from Date_created) as mth
  ,count(*) 
from Customer
group by
   extract(year from Date_created) as yr
  ,extract(month from Date_created) as mth
order by yr, mth

用您的 DBMS 中的匹配函数替换 EXTRACT，例如对于 SQL 服务器 datepart(year, date)

Answer 3

根据您的查询，我认为这样做会更简单：

SELECT COUNT (Name) FROM Customer WHERE MONTH(Date_created)= MONTH(GETDATE())

虽然我不确定这是否是您所期望的，因为您的问题可以用多种方式解释

编辑：考虑到不同年份：

SELECT COUNT (Name) FROM Customer 
WHERE MONTH(Date_created)= MONTH(GETDATE())
AND YEAR(Date_created)= YEAR(GETDATE())

Answer 4

我不喜欢将 BETWEEN 与日期一起使用（请参阅此博客 What do BETWEEN and the Devil Have in Common）。但是，您查询的问题是日期顺序错误。较小的值必须先行：

SELECT COUNT(Name) 
FROM Customer 
WHERE Date_created BETWEEN CONVERT(date, getdate() - 30) AND CONVERT(date, getdate())

最好写成：

SELECT COUNT(Name)
FROM Customer
WHERE Date_Created >= CONVERT(date, getdate() - 30) AND
      Date_Created < CONVERT(date, getdate());

我不确定这是否满足您对“月”的定义，但至少查询将 return 30 天的创建。

试图获得一个 SQL 命令来获取每个月的新客户，但我似乎无法让它工作

Trying to get an SQL command that gets the new customers from each month but i cant seem to get it working

sql

sql-server

labview