tailieunhanh - Functional Dependencies and Normalization for Relational Databases

GUIDELINE 3: Relations should be designed such that their tuples will have as few NULL values as possible Attributes that are NULL frequently could be placed in separate relations (with the primary key) Reasons for nulls: attribute not applicable or invalid attribute value unknown (may exist) value known to exist, but unavailable | Functional Dependencies and Normalization for Relational Databases(phu thuoc ham va chuan hoa CSDL quan he) 5/14/2020 12:25:36 AM Chapter Outline(chuong mo dau) 1 Informal Design Guidelines for Relational Databases(huong dan thiet ke thong tin cho co so du lieu quan he) Semantics of the Relation Attributes Redundant Information in Tuples and Update Anomalies Null Values in Tuples Spurious Tuples 2 Functional Dependencies (FDs) Definition of FD Inference Rules for FDs Equivalence of Sets of FDs Minimal Sets of FDs Chapter Outline(contd.) 3 Normal Forms Based on Primary Keys(chuan co ban trong nhung khoa chinh) Normalization of Relations (chuan hoa quan he) Practical Use of Normal Forms () Definitions of Keys and Attributes Participating in Keys(dinh nghia ve khoa va cac thanh phan thuoc tinh cua khoa) First Normal Form(chuan co ban 1) Second Normal Form(chuan co ban 2) Third Normal Form(chuan co ban 3) 4 General Normal Form | Functional Dependencies and Normalization for Relational Databases(phu thuoc ham va chuan hoa CSDL quan he) 5/14/2020 12:56:37 AM Chapter Outline(chuong mo dau) 1 Informal Design Guidelines for Relational Databases(huong dan thiet ke thong tin cho co so du lieu quan he) Semantics of the Relation Attributes Redundant Information in Tuples and Update Anomalies Null Values in Tuples Spurious Tuples 2 Functional Dependencies (FDs) Definition of FD Inference Rules for FDs Equivalence of Sets of FDs Minimal Sets of FDs Chapter Outline(contd.) 3 Normal Forms Based on Primary Keys(chuan co ban trong nhung khoa chinh) Normalization of Relations (chuan hoa quan he) Practical Use of Normal Forms () Definitions of Keys and Attributes Participating in Keys(dinh nghia ve khoa va cac thanh phan thuoc tinh cua khoa) First Normal Form(chuan co ban 1) Second Normal Form(chuan co ban 2) Third Normal Form(chuan co ban 3) 4 General Normal Form Definitions (For Multiple Keys)(dinh nghia chuan co ban chung)(cho nhieu khoa) 5 BCNF (Boyce-Codd Normal Form)(chuan co ban boyce-codd) 1 Informal Design Guidelines for Relational Databases (1) What is relational database design?(thiet ke co so du lieu quan he la gi ?) The grouping of attributes to form "good" relation schemas(nhom cac thuoc tinh tu so do quan he tot) Two levels of relation schemas(2 cap cua so do quan he) The logical "user view" level(cap “khung nhin cho nguoi su dung”). The storage "base relation" level(cap luu tru “quan he co ban”). Design is concerned mainly with base relations What are the criteria for "good" base relations? Informal Design Guidelines for Relational Databases (2) We first discuss informal guidelines for good relational design Then we discuss formal concepts of functional dependencies and normal forms - 1NF (First Normal Form) - 2NF (Second Normal Form) - 3NF (Third Normal Form) - BCNF (Boyce-Codd Normal Form) Additional types of dependencies,