barcode font excel free download Silberschatz Korth Sudarshan: Database System Concepts, Fourth Edition in Software

Painting Code 128 Code Set C in Software Silberschatz Korth Sudarshan: Database System Concepts, Fourth Edition

Silberschatz Korth Sudarshan: Database System Concepts, Fourth Edition
Code 128C Maker In None
Using Barcode creator for Software Control to generate, create ANSI/AIM Code 128 image in Software applications.
Scanning Code 128 Code Set B In None
Using Barcode decoder for Software Control to read, scan read, scan image in Software applications.
II Relational Databases
Code 128 Code Set A Creator In C#.NET
Using Barcode printer for VS .NET Control to generate, create USS Code 128 image in .NET framework applications.
Creating Code 128 Code Set A In VS .NET
Using Barcode encoder for ASP.NET Control to generate, create Code 128 Code Set A image in ASP.NET applications.
7 Relational Database Design
Code128 Generation In .NET Framework
Using Barcode generation for .NET Control to generate, create Code 128C image in VS .NET applications.
Code 128 Code Set B Printer In VB.NET
Using Barcode generation for .NET Control to generate, create Code 128C image in VS .NET applications.
The McGraw Hill Companies, 2001
Draw Barcode In None
Using Barcode creator for Software Control to generate, create barcode image in Software applications.
Drawing Bar Code In None
Using Barcode creator for Software Control to generate, create bar code image in Software applications.
7
Code 128 Code Set C Printer In None
Using Barcode encoder for Software Control to generate, create Code 128 Code Set C image in Software applications.
Creating EAN / UCC - 13 In None
Using Barcode generator for Software Control to generate, create EAN-13 image in Software applications.
Relational-Database Design
Printing UCC - 12 In None
Using Barcode generator for Software Control to generate, create UPC-A Supplement 5 image in Software applications.
Painting Code 39 Extended In None
Using Barcode maker for Software Control to generate, create Code 3/9 image in Software applications.
The domain of all integers would be nonatomic if we considered each integer to be an ordered list of digits As a practical illustration of the above point, consider an organization that assigns employees identi cation numbers of the following form: The rst two letters specify the department and the remaining four digits are a unique number within the department for the employee Examples of such numbers would be CS0012 and EE1127 Such identi cation numbers can be divided into smaller units, and are therefore nonatomic If a relation schema had an attribute whose domain consists of identi cation numbers encoded as above, the schema would not be in rst normal form When such identi cation numbers are used, the department of an employee can be found by writing code that breaks up the structure of an identi cation number Doing so requires extra programming, and information gets encoded in the application program rather than in the database Further problems arise if such identi cation numbers are used as primary keys: When an employee changes department, the employee s identi cation number must be changed everywhere it occurs, which can be a dif cult task, or the code that interprets the number would give a wrong result The use of set valued attributes can lead to designs with redundant storage of data, which in turn can result in inconsistencies For instance, instead of the relationship between accounts and customers being represented as a separate relation depositor, a database designer may be tempted to store a set of owners with each account, and a set of accounts with each customer Whenever an account is created, or the set of owners of an account is updated, the update has to be performed at two places; failure to perform both updates can leave the database in an inconsistent state Keeping only one of these sets would avoid repeated information, but would complicate some queries Set valued attributes are also more complicated to write queries with, and more complicated to reason about In this chapter we consider only atomic domains, and assume that relations are in rst normal form Although we have not mentioned rst normal form earlier, when we introduced the relational model in 3 we stated that attribute values must be atomic Some types of nonatomic values can be useful, although they should be used with care For example, composite valued attributes are often useful, and set valued attributes are also useful in many cases, which is why both are supported in the E-R model In many domains where entities have a complex structure, forcing a rst normal form representation represents an unnecessary burden on the application programmer, who has to write code to convert data into atomic form There is also a runtime overhead of converting data back and forth from the atomic form Support for nonatomic values can thus be very useful in such domains In fact, modern database systems do support many types of nonatomic values, as we will see in s 8 and 9 However, in this chapter we restrict ourselves to relations in rst normal form
Paint Leitcode In None
Using Barcode generation for Software Control to generate, create Leitcode image in Software applications.
Generating ANSI/AIM Code 39 In None
Using Barcode maker for Word Control to generate, create Code-39 image in Office Word applications.
72 Pitfalls in Relational-Database Design
GS1 - 13 Reader In VB.NET
Using Barcode decoder for Visual Studio .NET Control to read, scan read, scan image in .NET applications.
Code 3 Of 9 Encoder In Java
Using Barcode generation for Java Control to generate, create Code-39 image in Java applications.
Before we continue our discussion of normal forms, let us look at what can go wrong in a bad database design Among the undesirable properties that a bad design may have are:
Code 3 Of 9 Creator In .NET Framework
Using Barcode printer for VS .NET Control to generate, create Code-39 image in VS .NET applications.
Bar Code Creation In None
Using Barcode generator for Online Control to generate, create bar code image in Online applications.
Silberschatz Korth Sudarshan: Database System Concepts, Fourth Edition
Creating GS1 - 12 In None
Using Barcode generation for Online Control to generate, create UPC Symbol image in Online applications.
Drawing Linear Barcode In .NET Framework
Using Barcode printer for VS .NET Control to generate, create Linear image in Visual Studio .NET applications.
II Relational Databases
7 Relational Database Design
The McGraw Hill Companies, 2001
Pitfalls in Relational-Database Design
Repetition of information Inability to represent certain information We shall discuss these problems with the help of a modi ed database design for our banking example: In contrast to the relation schema used in s 3 to 6, suppose the information concerning loans is kept in one single relation, lending, which is de ned over the relation schema Lending-schema = (branch-name, branch-city, assets, customer-name, loan-number, amount) Figure 71 shows an instance of the relation lending (Lending-schema) A tuple t in the lending relation has the following intuitive meaning: t[assets] is the asset gure for the branch named t[branch-name] t[branch-city] is the city in which the branch named t[branch-name] is located t[loan-number] is the number assigned to a loan made by the branch named t[branch-name] to the customer named t[customer-name] t[amount] is the amount of the loan whose number is t[loan-number] Suppose that we wish to add a new loan to our database Say that the loan is made by the Perryridge branch to Adams in the amount of $1500 Let the loan-number be L-31 In our design, we need a tuple with values on all the attributes of Lendingschema Thus, we must repeat the asset and city data for the Perryridge branch, and must add the tuple (Perryridge, Horseneck, 1700000, Adams, L-31, 1500) customername Jones Smith Hayes Jackson Jones Turner Williams Hayes Johnson Glenn Brooks loannumber L-17 L-23 L-15 L-14 L-93 L-11 L-29 L-16 L-18 L-25 L-10
branch-name Downtown Redwood Perryridge Downtown Mianus Round Hill Pownal North Town Downtown Perryridge Brighton
branch-city Brooklyn Palo Alto Horseneck Brooklyn Horseneck Horseneck Bennington Rye Brooklyn Horseneck Brooklyn Figure 71
Copyright © OnBarcode.com . All rights reserved.