barcode vb.net 2010 Alternative Summary Designs in Software

Generator QR Code JIS X 0510 in Software Alternative Summary Designs

Alternative Summary Designs
QR Code JIS X 0510 Decoder In None
Using Barcode Control SDK for Software Control to generate, create, read, scan barcode image in Software applications.
Encode QR Code JIS X 0510 In None
Using Barcode drawer for Software Control to generate, create QR Code 2d barcode image in Software applications.
A dimensional aggregate schema that conforms to the base schema is but one way to organize the storage of summary data. Derived tables, as described in the previous chapter, may provide a useful alternative. A single-table design, on the other hand, is likely to lead to trouble.
Scanning Quick Response Code In None
Using Barcode recognizer for Software Control to read, scan read, scan image in Software applications.
QR Code Maker In C#.NET
Using Barcode generation for VS .NET Control to generate, create Denso QR Bar Code image in VS .NET applications.
Transformative Summaries May Also Be Useful
Printing QR Code In Visual Studio .NET
Using Barcode encoder for ASP.NET Control to generate, create QR Code JIS X 0510 image in ASP.NET applications.
Print Quick Response Code In VS .NET
Using Barcode creation for .NET Control to generate, create QR Code image in VS .NET applications.
As defined in this chapter, an aggregate schema is a very specific form of summarization: one that conforms to the original, base schema. Data can be summarized in other ways that do not preserve the organizational structure of the base data. These too are valid summaries. Since they transform the structure of the base data they summarize, they are examples of derived schemas, as discussed in 14. As you have learned, the tables in an aggregate schema conform to those in the base schema it summarizes. The aggregate facts have the same name, meaning, and content as those in the base fact table; dimension tables are the same as those in the base star, or are conformed rollups whose attributes share the name, meaning, and content of those in the base star. This conformance ensures semantic consistency across stars and facilitates a simple query-rewriting process. A summary that transforms the structure or meaning of the original data may also be of value. Its content, by definition, does not conform to the original schema. It may contain a fact that is not present in the original star, exclude certain data, or require a different query structure. Summaries that transform the original dimensional structure in any of these ways are examples of derived schemas. TiP A summary that transforms the structure of the base star is a derived schema rather than an aggregate. It may provide useful performance benefits. A query that takes advantage of a derived schema will differ in structure from one against the base schema. Several examples of stars that transform the dimensional structure of a schema were provided in 14. These included snapshots that were derived from transactions, and accumulating snapshots that correlate disparate activities. By restructuring information in advance, these stars made certain forms of reporting much easier. Although they may
QR-Code Drawer In Visual Basic .NET
Using Barcode creator for .NET framework Control to generate, create QR Code image in .NET applications.
Painting Data Matrix In None
Using Barcode creator for Software Control to generate, create Data Matrix image in Software applications.
15 Aggregates 363
Code 128C Maker In None
Using Barcode creator for Software Control to generate, create Code 128B image in Software applications.
EAN-13 Supplement 5 Creator In None
Using Barcode generator for Software Control to generate, create UPC - 13 image in Software applications.
summarize the original table, they require that queries be written differently. For this reason, they are not classified as aggregates. Additional examples of derived stars in 14 merged data from multiple fact tables, transposed row-wise and column-wise fact storage, took slices of fact tables, or precomputed comparisons using set operations or subqueries. Each in some way transforms the structure of the base schema, requires queries to be written differently, and alters the nature of the query results. While some of these derived tables summarize the original data sets, they are not considered to be aggregate schemas in the sense defined in this chapter. They may, however, be valuable additions to the dimensional model. Earlier in this chapter, an example was provided that could not be aided by a dimensional aggregate. Filtering a query so it only includes order lines with a dollar amount that is greater than $500 requires access to the granular detail, even if results are highly summarized. An aggregate will not include the necessary detail to perform this filtering. However, it is still possible to compute this information and store the result in a derived schema. In the derived schema, a fact similar to the original order_dollars will be recorded. Because it represents the dollar amount only for high-value orders, the summary fact will return different results. It does not conform to the original fact and should be given a new and unique name, such as high_value_order_dollars.
Making Code 39 Full ASCII In None
Using Barcode encoder for Software Control to generate, create USS Code 39 image in Software applications.
Generate Bar Code In None
Using Barcode generator for Software Control to generate, create barcode image in Software applications.
Single Table Designs Should Be Avoided
Draw UPC Shipping Container Symbol ITF-14 In None
Using Barcode maker for Software Control to generate, create DUN - 14 image in Software applications.
Draw Matrix 2D Barcode In C#.NET
Using Barcode creator for .NET framework Control to generate, create Matrix Barcode image in Visual Studio .NET applications.
One alternative manner of storing summary information is less likely to prove an asset to the dimensional model. When a single fact table is called on to store both detailed and summarized data, the result may appear compact and neat, but a potential problem arises. It becomes possible, and in fact likely, that the aggregate will be misused, producing inaccurate results. A single fact table design seeks to simplify the storage of aggregates by storing summarized data together with the detail, rather than in separate tables. For example, an orders star might be called upon to house both daily order information and monthly summaries. In order to make this work, it will be necessary to construct a time dimension table that can represent either a month or a day. Figure 15-6 provides an example. Each row in the day table represents either a day or a month. A column called level is used to indicate what each row represents. It takes on the values Month or Day. Not all the attributes of the table apply to months; those that do not default to a preselected value such as N/A for textual data. The shaded row shows what this looks like for the row that represents January 2009. Some designers prefer to use NULL values for nonapplicable columns, although these can lead to problems at query time, as you learned in 6. This multipurpose dimension table makes it possible to store monthly summaries in the same fact table that records daily data. The fact table includes a day_key. For rows that contain daily data, this key will refer to a dimension row that represents a day. For rows that contain monthly data, it will refer to a dimension row that represents a month. In this scenario, a query can make use of the monthly aggregates by adding a constraint like this one:
Scan Code39 In C#
Using Barcode decoder for .NET framework Control to read, scan read, scan image in .NET applications.
Reading GS1 - 12 In VS .NET
Using Barcode decoder for .NET framework Control to read, scan read, scan image in .NET applications.
WHERE day.level = "month"
Generating Code39 In Visual C#.NET
Using Barcode creator for .NET framework Control to generate, create Code 39 Extended image in .NET framework applications.
Encode Code 128A In None
Using Barcode printer for Office Word Control to generate, create ANSI/AIM Code 128 image in Office Word applications.
A query that focuses on the daily detail includes a constraint like this one:
Encoding GTIN - 128 In Objective-C
Using Barcode maker for iPad Control to generate, create UCC-128 image in iPad applications.
Recognize EAN-13 In Java
Using Barcode scanner for Java Control to read, scan read, scan image in Java applications.
WHERE day.level = "Day"
Copyright © OnBarcode.com . All rights reserved.