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Preparation for labsession 1
Study chapter 3 of the database book, up to and including section 3.2.2.
- 3.1 explains the basics of the relational database model. It briefly recalls the relationship between the E-R model and the relational model.
- 3.2 describes the relational algebra. The operators are introduced and described in 3.2.1, and relational algebra expressions are defined in 3.2.2.
Notes:
During the first labsession you will be given exercises on the basic operators of the relational algebra. You must have studied chapter 3 of the database book up to section 3.2.2 in order to be able to answer the questions of the labsession.
In Section 3.1 the relational database model is described. We assume that you already know how to do database design using the entity-relationship model and translate E-R diagrams to relational schemas. Section 3.1 recalls this briefly, and describes keys, strong and weak entity sets, combining tables, dealing with multivalued attributes, etc.
Section 3.2.1 defines the basic operations of the relational algebra. It gives examples of English questions, translated into the relational algebra. In the labsession we will give you many more questions to translate, and in the next colstruction we will do more of that, with more difficult questions. You should make sure that you studied sections 3.2.1 and 3.2.2 and that you understand why the given relational algebra expressions are correct translations of the given questions.