Discrete Math Notes:
Chapter 8: Applications of Discrete Mathematics
8.3 N-ary relations and relational databases
n-ary relation, relation on n sets
database, a large collection of data records that is searched and manipulated by a computer.
relational database model, stores data records as relations
attribute, the type of data stored in each entry of the n-tuple
query, a database is a request for a particular set of data.
Key, an attribute or set of attributes that uniguely identifies each n-tuple in the database.
Extended Euclidean Algorithm, The algorithm used to find the coefficients, s and t, such that gcd(x, y) = sx + ty
multiplicative inverse mod n, is an integer s {1, 2, .., n-1} such that sx mod n = 1.
Overview:
A database is a huge collection of data records that a computer can search and change. Data records are stored as relations in the relational database model. An attribute refers to the type of data recorded in each n-tuple element. A database query is a request for a specific collection of data. Each n-tuple in the database is uniquely identified by a key, which is an attribute or group of attributes. The selection operation selects n-tuples from a relational database that satisfy certain attribute constraints. In each of the n-tuples, the projection operation takes a subset of the attributes and deletes all of the others.