Question

Relation are closed under algebra. Justify your answer

Answer 1

Answer:

Step-by-step explanation:

Having defined the relvars in the suppliers-and-parts database (see Chapter 3), and having “loaded” or initialized them (again, see Chapter 3), we can now start to use them for “real work.” More specifically, we can now issue queries—i.e., retrieval requests—against those relvars, using operators of what’s called the relational algebra, and in this chapter I want to start our investigation into those operators. Caveat: The chapter is, regrettably, quite long, and you might want to take it a piece at a time. To help you in this regard, I haven’t left all of the exercises and answers to the very end of the chapter but have instead interspersed them at intervals among the regular explanatory text.