select-用MySql的Navicat創建存儲過程總是報1458錯誤

用MySql的Navicat創建存儲過程總是報1458錯誤

下面是我穿件存儲過程的代碼。求大神幫忙看看。真心很急，明天就要用。

 create procedure searchStudentGrade(in id char)
 begin
     if id is null
         select  student.StudentID,student.StudentName,student.ClassNumber,grade.ExamID,course.CourseName,grade.Grade,course.CourseID
        from student,grade,course
        where student.StudentID=grade.StudentID and grade.CourseID=course.CourseID;
    else
        select student.StudentID,student.StudentName,student.ClassNumber,grade.ExamID,course.CourseName,grade.Grade,course.CourseID
        from student,grade,course
        where student.StudentID=grade.StudentID and grade.CourseID=course.CourseID and grade.StudentID=id;
    end if;
end;

最佳回答：

 create procedure searchStudentGrade(in id char)
 begin
     if id is null then 這裡少了一個then吧
         select  student.StudentID,student.StudentName,student.ClassNumber,grade.ExamID,course.CourseName,grade.Grade,course.CourseID
        from student,grade,course
        where student.StudentID=grade.StudentID and grade.CourseID=course.CourseID;
    else
        select student.StudentID,student.StudentName,student.ClassNumber,grade.ExamID,course.CourseName,grade.Grade,course.CourseID
        from student,grade,course
        where student.StudentID=grade.StudentID and grade.CourseID=course.CourseID and grade.StudentID=id;
    end if;
end;