Tài liệu Pro SQL Sever 2012 Relational Database Design and Implementation ppt

[...]... between relational the relational data structures introduced in the relational data structures section • Dependencies: The concept of dependencies between values and how they shape the process of designing databases later in the book will be discussed • Relational programming: This section will cover the differences between functional programming using C# or VB (Visual Basic) and relational programming... (Visual Basic) and relational programming using SQL (Structured Query Language) • Database design phases: This section provides an overview of the major phases of relational database design: conceptual/logical, physical, and storage For time and budgetary reasons, you might be tempted to skip the first database design phase and move straight to the physical implementation phase However, skipping any or... commit, and rollback) This rule mandates the existence of a relational database language, such as SQL, to manipulate data The language must be able to support all the central functions of a DBMS: creating a database, retrieving and entering data, implementing database security, and so on SQL as such isn’t specifically required, and other experimental languages are in development all of the time, but SQL. .. UNKNOWN TRUE Table 1-5 AND and OR Truth Table Operand1 Operand2 Operand1 AND Operand2 Operand1 OR Operand2 TRUE TRUE TRUE FALSE FALSE TRUE FALSE UNKNOWN FALSE UNKNOWN TRUE FALSE UNKNOWN FALSE FALSE TRUE TRUE TRUE FALSE UNKNOWN 15 CHAPTER 1 ■ The Fundamentals In this introductory chapter, my main goal is to point out that NULLs exist and are part of the basic foundation of relational databases (along with... getting you started to understand why relational database are implemented as they are today In three papers, Codd took a major step forward in defining what a relational database is and how it is supposed to be used In the early days, Codd’s 12 rules were used to determine whether a database vendor could call itself relational and presented stiff implementation challenges for database developers As you... are most important and provide common useful constructs to help you start developing great databases quickly Recognizing Relational Data Structures This section introduces the following core relational database structures and concepts: • Database and schema • Tables, rows, and columns • Missing values (nulls) • Uniqueness constraints (keys) As a person reading this book, this is probably not your first... constraints In 1989, the SQL- 89 specification was adopted, and it included referential integrity, which was a tremendous improvement and a move toward implementing Codd’s twelfth rule (see Handbook on Architectures of Information Systems by Bernus, Mertins, and Schmidt [Springer 2006]) Several more versions of the SQL standard have come and gone, in 1992, 1999, 2003, 2006, and 2008 For the most part,... started with design is that they elucidate why SQL Server and other relational engine based database systems work the way they do Rule 1: The Information Principle All information in the relational database is represented in exactly one and only one way—by values in tables 3 CHAPTER 1 ■ The Fundamentals While this rule might seem obvious after just a little bit of experience with relational databases,... you, but there are some common misunderstandings in their usage that can make the difference between a mediocre design and a high-class, professional one In particular, misunderstanding the vital role of keys in the database can lead to severe data integrity issues and to the mistaken belief that such keys and constraints can be effectively implemented outside the database (Here is a subtle hint: they... piece of data ? Now you have to find a new stand-in for NULL and go back and change all of the code, and that is a pain You have eliminated one troublesome but well-known problem of dealing with three-value logic and replaced it with a problem that now requires all of your code to be written using a nonstandard pattern What makes this implementation using a stand-in value to represent NULL more difficult . strictly database programmers or a programmer that has never used a relational database product before to learn why relational databases are designed. and hardware has continued up and up as the years progress. e biggest changes to SQL Server 2012 for the relational programmer lie in some of the T-SQL