问题描述
我有以下查询返回过去 7 天内输入的图书数量。是否可以修改查询,使其只返回自一周开始以来输入的次数?
public int GetWeeklyCount()
{
var week = DateTime.Today.AddDays(-7);
return database.ExecuteScalar<int>("SELECT count(*) FROM Book WHERE bookEntryTime > ?;",week);
}
解决方法
人们对一周开始的含义各不相同,但例如,如果您认为一周从星期一开始:
var week = DateTime.Today;
while(week.DayOfWeek != DayOfWeek.Monday)
week = week.AddDays(-1);
return database.ExecuteScalar<int>("SELECT count(*) FROM Book WHERE bookEntryTime > ?;",week);
你也可以直接进入数学:
var week = DateTime.Today.AddDays(-(((int)DateTime.Today.DayOfWeek+6)%7));
return database.ExecuteScalar<int>("SELECT count(*) FROM Book WHERE bookEntryTime > ?;",week);
但对我来说,它是相对非自记录的,性能优势很小