SQL and Relational Theory, 2nd Edition

EXERCISES

1.1 (Repeated from the body of the chapter, but slightly reworded here.) If you haven’t done so already, go through the chapter again and identify all of the places where I used the term relation when I should by rights have used the term relvar instead.

1.2 Who was E. F. Codd?

1.3 What’s a domain?

1.4 What do you understand by the term referential integrity?

1.5 The terms heading, body, attribute, tuple, cardinality, and degree, defined in the body of the chapter for relation values, can all be interpreted in the obvious way to apply to relvars as well. Make sure you understand this remark.

1.6 Distinguish between the two meanings of the term data model.

1.7 Explain in your own words (a) physical data independence, (b) the difference between model and implementation.

1.8 In the body of the chapter, I said that tables like those in Figure 1-1 and Figure 1-3 weren’t relations as such but, rather, pictures of relations. What are some of the specific points of difference between such pictures and the corresponding relations?

1.9 (Try this exercise without looking back at the body of the chapter.) What relvars does the suppliers-and-parts database contain? What attributes do they involve? What keys and foreign keys do they have? (The point of this exercise is that it’s worth making yourself as familiar as possible with the structure, at least in general terms, of the running example. It’s not so important to remember the actual data values in detail—though it wouldn’t hurt if you ...