CREATE PROCEDURE dbo.EnrollStudent ( @CourseID  AS INTEGER,
                                     @StudentID AS VARCHAR(20) ) AS
BEGIN
   DECLARE @StatusID INTEGER
   DECLARE @Status VARCHAR(50)
   DECLARE @CurrentSeats INTEGER
   DECLARE @ErrorCode INTEGER
   SET @StatusID=0



      IF EXISTS (SELECT 1
                    FROM dbo.CourseEnrollment
                    WHERE dbo.CourseEnrollment.CourseId=@CourseID AND dbo.CourseEnrollment.StudentId=@StudentID )
        BEGIN

         BEGIN TRAN Tr1
         SET @StatusID = 1
         SELECT @ErrorCode=@@ERROR
         IF (@ErrorCode<>0) GOTO OTHERPROBLEM
         ELSE
         COMMIT TRAN Tr1

        END


     IF EXISTS ( SELECT 1
                    FROM dbo.CourseEnrollment
                    FULL OUTER JOIN dbo.Courses
                    ON dbo.Courses.CourseId=@CourseID
                    WHERE dbo.CourseEnrollment.StudentId<>@StudentID  AND dbo.Courses.Faculty IS NULL )
            BEGIN
            BEGIN TRAN Tr2
                SET @StatusID=2
                SELECT @ErrorCode=@@ERROR
                 IF (@ErrorCode<>0) GOTO OTHERPROBLEM2
                 ELSE
                 COMMIT TRAN Tr2

                 END



    IF @StatusID=0
    BEGIN
        IF EXISTS ( SELECT 1
                    FROM dbo.Courses
                    WHERE dbo.Courses.CourseId=@CourseID AND dbo.Courses.Faculty IS NOT NULL )

                BEGIN


                BEGIN TRAN Tr3

                SET @StatusID=3


                BEGIN TRAN InsertingValues
                INSERT INTO dbo.CourseEnrollment (dbo.CourseEnrollment.StudentId,dbo.CourseEnrollment.CourseId)
                                                VALUES          (@StudentID,@CourseID);

                SELECT @ErrorCode=@@ERROR
                 IF (@ErrorCode<>0) GOTO InsertProblem
                 ELSE
                 COMMIT TRAN InsertingValues




                BEGIN TRAN UpdateCourses
                UPDATE dbo.Courses
                    SET OpenSeats = OpenSeats-1
                       WHERE dbo.Courses.CourseId = @CourseID

                SELECT @ErrorCode=@@ERROR
                 IF (@ErrorCode<>0) GOTO UpdateProblem
                 ELSE
                 COMMIT TRAN UpdateCourses




                SELECT @CurrentSeats=OpenSeats
                    FROM dbo.Courses
                        WHERE dbo.Courses.CourseId = @CourseID

                        IF (@CurrentSeats<0) GOTO PROBLEM
                        ELSE
                        COMMIT TRAN Tr3


                END

    END



    OTHERPROBLEM:
         BEGIN
            PRINT 'Unable to set status'
            ROLLBACK TRAN
         END


    OTHERPROBLEM2:
                 BEGIN
                     PRINT 'Unable to set status'
                     ROLLBACK TRAN
                 END


     UpdateProblem:
                 BEGIN
                     PRINT 'Not able to update values'
                     ROLLBACK TRAN InsertingValues
                 END



    InsertProblem:
                 BEGIN
                     PRINT 'Not able to insert'
                     ROLLBACK TRAN InsertingValues
                 END



    PROBLEM:
                BEGIN
                    PRINT 'Seats Full!'
                    ROLLBACK TRAN
                END




     IF @StatusID = 1
        BEGIN
         SET @Status = 'The Student is already enrolled'
        END;

     ELSE IF @StatusID = 2
         BEGIN
            SET @Status = 'Cannot enroll until faculty is selected'
         END

     ELSE IF @StatusID = 3
         BEGIN
            SET @Status = 'Student Enrolled'
        END

   SELECT @Status

END;

(1 row(s) affected)

(1 row(s) affected)
Unable to set status
Msg 3903, Level 16, State 1, Procedure EnrollStudent, Line 101
The ROLLBACK TRANSACTION request has no corresponding BEGIN TRANSACTION.
Unable to set status
Msg 3903, Level 16, State 1, Procedure EnrollStudent, Line 108
The ROLLBACK TRANSACTION request has no corresponding BEGIN TRANSACTION.
Not able to update values
Msg 3903, Level 16, State 1, Procedure EnrollStudent, Line 115
The ROLLBACK TRANSACTION request has no corresponding BEGIN TRANSACTION.
Not able to insert
Msg 3903, Level 16, State 1, Procedure EnrollStudent, Line 123
The ROLLBACK TRANSACTION request has no corresponding BEGIN TRANSACTION.
Seats Full!
Msg 3903, Level 16, State 1, Procedure EnrollStudent, Line 131
The ROLLBACK TRANSACTION request has no corresponding BEGIN TRANSACTION.

(1 row(s) affected)

BEGIN TRANSACTION;
BEGIN TRY

   --execute all your stored proc code here and then commit
   COMMIT;

END TRY
BEGIN CATCH

   --if an exception occurs execute your rollback, also test that you have had some successful transactions
   IF @@TRANCOUNT > 0 ROLLBACK;

END CATCH

BEGIN TRAN Tr1

-- your code

ROLLBACK TRAN Tr1