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I think you might be making your life more complicated by conflating the requirement of your database with the process of meeting that requirement. Databases are a static representation of your busine …

While you've done a pretty thorough job of following the textbook requirements, there are some practical considerations that you might or might not want to include, depending on the expectations of th …

In addition to what Michael Green has pointed out in his excellent answer, you should also be aware of optimistic concurrency which is an application-level technique in a database that is used to guar …

The problem statement says: You decide to model a CONTACT table with primary key of Teacher-ID and Contact-Info, which is the contact information itself. Your solution doesn't do this, which is why y …

Transactional data that is highly structured is a perfect fit for relational databases. It's not a matter of scale, it's a matter of what fits your data. NoSQL databases are for unstructured (or hig …

The question you should be asking is whether product attribute changes in general are of interest or if you are particularly concerned with changes in price. What you probably really want is to record …

The answer is, as usual, it depends, in this case, primarily on whether your values are subject to change. Although there are lots of competing principles, the primary principle at play is that in a r …

If the relationship between TableA and TableB is meant to be one-to-many then you don't need a third table (TableC). However, if TableA to TableB are meant to have a many-to-many relationship, then yo …

Using the English terms for your tables... There is not a many-to-many relationship between ORDER and PRODUCT. Each order has only one product, because ORDER.Product_ID depends on ORDER.Order_Number …

The associative entity idea is a good way to handle this, but it has a drawback that you might want to consider. Something that hasn't been addressed in some other answers is how you're going to main …

What you want to think about is what attributes you would track at each of the levels ("store" and "branch")? You don't want to repeat information in multiple places or have ambiguity around which …

Your definition of 2NF is not quite correct. 2NF is when a relation is in 1NF and it has no partial dependencies, meaning there are no predicates (columns) that depend on only part of a multi-part …

If your database supports it, you can use a table level CHECK constraint to compare two columns to make sure that they're equal. You could have a single CHECK constraint that confirms the course_id a …

What I recommend is separating out the concern of "Who are people we've heard of?" from the concern of "Who can get into the system now and how do they do that?" What this means in practice is that y …

Option 3 is considered the best practice in this case because it lets the RDBMS do what it is designed to do. You have the best options for controlling relationships with declarative referential integ …