从不同的表中检索数据（SQL Server）

Question

I have 4 tables in a SQL Server database with following schema:

1. Attendance

    CREATE TABLE [dbo].[Attendance] ( [AttendanceId] UNIQUEIDENTIFIER DEFAULT (newid()) NOT NULL, [CourseId] UNIQUEIDENTIFIER NOT NULL, [StudentId] UNIQUEIDENTIFIER NOT NULL, [SubjectId] UNIQUEIDENTIFIER NOT NULL, [Semester] INT NOT NULL, [Month] NVARCHAR (50) NOT NULL, [Count] INT NOT NULL, CONSTRAINT [PK_Attendance] PRIMARY KEY NONCLUSTERED ([AttendanceId] ASC), CONSTRAINT [FK_Attendance_Student] FOREIGN KEY ([StudentId]) REFERENCES [dbo].[Student] ([StudentId]) ); 

2. Course

    CREATE TABLE [dbo].[Course] ( [CourseId] UNIQUEIDENTIFIER DEFAULT (newid()) NOT NULL, [Name] NVARCHAR (50) NOT NULL, CONSTRAINT [PK_Course] PRIMARY KEY NONCLUSTERED ([CourseId] ASC) ); 

3. Student

    CREATE TABLE [dbo].[Student] ( [StudentId] UNIQUEIDENTIFIER DEFAULT (newid()) NOT NULL, [CourseId] UNIQUEIDENTIFIER NOT NULL, [Name] NVARCHAR (100) NOT NULL, [RollNo] INT NOT NULL, [Semester] INT NOT NULL, CONSTRAINT [PK_Student] PRIMARY KEY NONCLUSTERED ([StudentId] ASC), CONSTRAINT [FK_Student_Course] FOREIGN KEY ([CourseId]) REFERENCES [dbo].[Course] ([CourseId]) ); 

4. Subject

    CREATE TABLE [dbo].[Subject] ( [SubjectId] UNIQUEIDENTIFIER DEFAULT (newid()) NOT NULL, [CourseId] UNIQUEIDENTIFIER NOT NULL, [Name] NVARCHAR (100) NOT NULL, [Semester] INT NOT NULL, CONSTRAINT [PK_Subject] PRIMARY KEY NONCLUSTERED ([SubjectId] ASC), CONSTRAINT [FK_Subject_Course] FOREIGN KEY ([CourseId]) REFERENCES [dbo].[Course] ([CourseId]) ); 

I need to create a attendance report in the following format:

Course Name | Student Name | Subject Name | Semester | Month | Count

Please tell me what SQL Query I need to use and if there's any change in schema required then suggest the same.

I'm looking forward to have your replies.

Thanks,

Answer 1

You need to use a JOIN in your query so that it only returns rows which match a [StudentId] from the Attendance table.

eg

SELECT c.CourseName, s.StudentName, u.SubjectName, u.Semester, a.Month, a.Count
FROM Student s 
    JOIN Attendance a ON s.StudentId = a.StudentId
    JOIN Course c ON a.CourseId = c.CourseId
    JOIN Subject u ON c.CourseId = u.CourseId

Something along these lines will only return rows which specifically match