Deriving the Physical Model in Software

Printing Code 128 Code Set A in Software Deriving the Physical Model
Deriving the Physical Model
Generating USS Code 128 In Visual C#
Using Barcode printer for .NET Control to generate, create Code 128 Code Set A image in .NET framework applications.
was ready to go, we need to make a little change for consistency s sake Adding another relationship between tbl_address and tbl_employee allows us to store employee addresses in tbl_address Later, when we look at business rules, we will reconcile the fact that we now have two optional relationships in tbl_address Last, but not least, we have the subtype construct we modeled for payments As we discussed in 3, you have three options when you physically implement subtypes
Printing Code-128 In .NET
Using Barcode creator for ASP.NET Control to generate, create ANSI/AIM Code 128 image in ASP.NET applications.
Implement the supertype and all the subtypes in a single table Implement the subtypes as tables, and add the supertype data to each of these subtype tables Implement the supertype as a table and all the subtypes as additional tables
Print Code 128 Code Set A In VS .NET
Using Barcode creator for VS .NET Control to generate, create Code 128A image in .NET framework applications.
Which option you choose is dependent largely on the specific data you are working with In the case of Mountain View Music we will implement a single payment table that will contain all the data from each of the subtypes This decision is often driven by the number of attributes in each entity Because the only attributes common to all payments are the account holder and the payment type, we don t want that to be in its own table Especially with our addition of an address table, that would leave a payments table with two columns We could implement each payment as its own table, but that would be a relationship nightmare It would leave us with three separate relationships to order (depending on the payment type) and three relationships to address (one for each type) It is for these reasons that we decided to go with a single payment table This table will contain a relationship to address for the payment address and all the detail from each of the subtypes When you look at the payments table in Figure 99, you will probably notice that many of the columns are optional; that is, they allow NULL data That could lead to problems because we require certain pieces of information to, for example, process a credit card We will fix this problem a little later when we look at implementing business rules With that, we have looked at all the tables that are related to order and have created the foundation for the Orders submodel, as shown in Figure 910 These tables represent the bulk of the Mountain View Music database and were also a bit trickier to derive from our logical model We
Code 128A Maker In VB.NET
Using Barcode maker for VS .NET Control to generate, create Code 128A image in VS .NET applications.
9
Drawing Bar Code In VS .NET
Using Barcode maker for ASP.NET Control to generate, create bar code image in ASP.NET applications.
Creating the Physical Model
Barcode Recognizer In .NET
Using Barcode decoder for VS .NET Control to read, scan read, scan image in .NET framework applications.
FIGURE 99 The payment table implemented to model the Payments
Data Matrix Scanner In VS .NET
Using Barcode recognizer for .NET framework Control to read, scan read, scan image in .NET framework applications.
supertype in the Mountain View Music logical model
Print Code 3/9 In Visual Basic .NET
Using Barcode creation for .NET framework Control to generate, create Code39 image in .NET applications.
FIGURE 910 The beginning of the physical model for Mountain View Music s orders
DataMatrix Creation In .NET Framework
Using Barcode generator for .NET framework Control to generate, create DataMatrix image in .NET applications.
Deriving the Physical Model
Making Barcode In Java
Using Barcode printer for Java Control to generate, create barcode image in Java applications.
still have a couple of submodels to look at, but our physical model is quickly taking shape
Code 128 Generator In C#
Using Barcode creator for .NET framework Control to generate, create ANSI/AIM Code 128 image in .NET applications.
Web Session and Lists Submodel
Paint UCC - 12 In .NET Framework
Using Barcode encoder for .NET Control to generate, create EAN / UCC - 14 image in .NET framework applications.
Finally, we have two small submodels that we will look at together The Web Session submodel has only one new entity, Shopping Cart This entity acts as a join between Customers and Products so that customers can save items in their shopping carts on the Web site for later purchase This table is simple It holds the customer ID and the products that customers have in their cart In addition it tells us the quantity and the status of each product This entity is another simple table and is taken as is We also have the two tables used for lookup values: Lists and List Items These tables exist to provide the front-end application a place to store related lists of data such as order status or various product attributes Again, these tables are physically modeled as is, with only name changes to match our naming standards At this point we have looked at all the entities in the logical model and found homes for them in the physical model In the next section we look at getting the relationships modeled in the physical world as well as getting our primary keys in order and modeling columns based on the logical attributes
Barcode Encoder In VS .NET
Using Barcode encoder for .NET framework Control to generate, create bar code image in VS .NET applications.
Encode DataMatrix In VS .NET
Using Barcode creation for ASP.NET Control to generate, create DataMatrix image in ASP.NET applications.
Encode GTIN - 12 In .NET
Using Barcode encoder for ASP.NET Control to generate, create UPC-A Supplement 5 image in ASP.NET applications.
Generating Barcode In Visual C#
Using Barcode maker for .NET framework Control to generate, create barcode image in Visual Studio .NET applications.
Bar Code Generation In VS .NET
Using Barcode generator for Visual Studio .NET Control to generate, create barcode image in .NET applications.