DB-Lec 2: Rational Model (1)
Welcome file DB-Lecture 2: Relational Model(1) Definition : The relational model is very simple and elegant. A relational database is a collection of one or more relations, which are based on the relational model. A relation is a table with rows and columns. The major advantages of the relational model are its straightforward data representation and the ease with which even complex queries can be expressed. Owing to the great language SQL, the most widely used language for creating, manipulating, and querying relational database. I.Structure of Relational Databases 1.1.Basic Structure Formally, given sets D i ( i = 1 , . . . , n ) ( D i = a i j ∣ j = 1 , . . . k ) D_i(i=1,...,n) (D_i=a_{ij}|_{j=1,...k}) D i ( i = 1 , ... , n ) ( D i = a ij ∣ j = 1 , ... k ) , a relation r r r is a subset of D 1 × D 2 × . . . × D n D_1\times D_2\times ...\times D_n D 1 × D 2 × ... × D n — a Cartesian product of a list of domain D i D_i D i . ...