Hi , am designing a database using SQL server it's about a registration system so am having data about the student, which classes he is going to attend and who is teaching these classes the problem is that i can't find a design that complies with certain conditions:
1-I wanna make sure that the student doesn't choose the class twice.
2-I wanna make sure that the student doesn't or not allowed to choose a date for a class that he already has a class in.
And this my problem how will i design the tables and what constraints will i have.