mysql - SQL 语句总和

Question

嘿伙计们，我正在尝试总结这些表格，但我不知道我做错了什么

我的第一张桌子是：

Reserve
ReserveID   MembershipID   PlayerCount   Time    CourseID

我的第二张桌子是

Courses
CourseID   Name

我正在尝试的 sql 语句在这里：

Select Sum(Reserve.Player_Count)Total
From Reserve 
Left Join Courses 
On Courses.CourseID = Reserve.ReserveID 
Where Time = "2012-04-09 07:10:00" 
And Courses.Name = "Lake" (or I had Courses.CourseId = "1")

Answer 1

你似乎在混合别名。避免他们

Select Sum(Reserve.Player_Count)Total
From Reserve 
Left Join Courses 
On Courses.CourseID = Reserve.ReserveID 
Where Reserve.Time = "2012-04-09 07:10:00" 
--     ^ Right here  
And Courses.Name = "Lake" (or I had Courses.CourseId = "1")