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Database Refactoring
A database refactoring is a simple change to a database schema that improves its design while retaining both its behavioral and informational semantics. Database refactoring does not change the way data is interpreted or used and does not fix bugs or add new functionality. Every refactoring to a database leaves the system in a working state, thus not causing maintenance lags, provided the meaningful data exists in the production environment. A database refactoring is conceptually more difficult than a code refactoring; code refactorings only need to maintain behavioral semantics while database refactorings also must maintain informational semantics. A database schema is typically refactored for one of several reasons: # To develop the schema in an evolutionary manner in parallel with the evolutionary design of the rest of the system. # To fix design problems with an existing legacy database schema. Database refactorings are often motivated by the desire for database normaliza ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Database Schema
The database schema is the structure of a database described in a formal language supported by the database management system (DBMS). The term "schema" refers to the organization of data as a blueprint of how the database is constructed (divided into database tables in the case of relational databases). The formal definition of a database schema is a set of formulas (sentences) called integrity constraints imposed on a database. These integrity constraints ensure compatibility between parts of the schema. All constraints are expressible in the same language. A database can be considered a structure in realization of the database language. The states of a created conceptual schema are transformed into an explicit mapping, the database schema. This describes how real-world entities are modeled in the database. "A database schema specifies, based on the database administrator's knowledge of possible applications, the facts that can enter the database, or those of interest to the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Software Bug
A software bug is an error, flaw or fault in the design, development, or operation of computer software that causes it to produce an incorrect or unexpected result, or to behave in unintended ways. The process of finding and correcting bugs is termed " debugging" and often uses formal techniques or tools to pinpoint bugs. Since the 1950s, some computer systems have been designed to deter, detect or auto-correct various computer bugs during operations. Bugs in software can arise from mistakes and errors made in interpreting and extracting users' requirements, planning a program's design, writing its source code, and from interaction with humans, hardware and programs, such as operating systems or libraries. A program with many, or serious, bugs is often described as ''buggy''. Bugs can trigger errors that may have ripple effects. The effects of bugs may be subtle, such as unintended text formatting, through to more obvious effects such as causing a program to crash, freezing th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Code Refactoring
In computer programming and software design, code refactoring is the process of restructuring existing computer code—changing the '' factoring''—without changing its external behavior. Refactoring is intended to improve the design, structure, and/or implementation of the software (its '' non-functional'' attributes), while preserving its functionality. Potential advantages of refactoring may include improved code readability and reduced complexity; these can improve the source codes maintainability and create a simpler, cleaner, or more expressive internal architecture or object model to improve extensibility. Another potential goal for refactoring is improved performance; software engineers face an ongoing challenge to write programs that perform faster or use less memory. Typically, refactoring applies a series of standardized basic ''micro-refactorings'', each of which is (usually) a tiny change in a computer program's source code that either preserves the behavior of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Database Normalization
Database normalization or database normalisation (see spelling differences) is the process of structuring a relational database in accordance with a series of so-called normal forms in order to reduce data redundancy and improve data integrity. It was first proposed by British computer scientist Edgar F. Codd as part of his relational model. Normalization entails organizing the columns (attributes) and tables (relations) of a database to ensure that their dependencies are properly enforced by database integrity constraints. It is accomplished by applying some formal rules either by a process of ''synthesis'' (creating a new database design) or ''decomposition'' (improving an existing database design). Objectives A basic objective of the first normal form defined by Codd in 1970 was to permit data to be queried and manipulated using a "universal data sub-language" grounded in first-order logic. An example of such a language is SQL, though it is one that Codd regarded as seriou ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stored Procedure
A stored procedure (also termed proc, storp, sproc, StoPro, StoredProc, StoreProc, sp, or SP) is a subroutine available to applications that access a relational database management system (RDBMS). Such procedures are stored in the database data dictionary. Uses for stored procedures include data-validation (integrated into the database) or access-control mechanisms. Furthermore, stored procedures can consolidate and centralize logic that was originally implemented in applications. To save time and memory, extensive or complex processing that requires execution of several SQL statements can be saved into stored procedures, and all applications call the procedures. One can use nested stored procedures by executing one stored procedure from within another. Stored procedures may return result sets, i.e., the results of a SELECT statement. Such result sets can be processed using cursors, by other stored procedures, by associating a result-set locator, or by applications. Stored pr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Database Trigger
A database trigger is procedural code that is automatically executed in response to certain events on a particular table or view in a database. The trigger is mostly used for maintaining the integrity of the information on the database. For example, when a new record (representing a new worker) is added to the employees table, new records should also be created in the tables of the taxes, vacations and salaries. Triggers can also be used to log historical data, for example to keep track of employees' previous salaries. Triggers in DBMS Below follows a series of descriptions of how some popular DBMS support triggers. Oracle In addition to triggers that fire (and execute PL/SQL code) when data is modified, Oracle 10g supports triggers that fire when schema-level objects (that is, tables) are modified and when user logon or logoff events occur. Schema-level triggers * After Creation * Before Alter * After Alter * Before Drop * After Drop * Before Insert The four main types of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Evolutionary Database Design
Evolutionary database design involves incremental improvements to the database schema so that it can be continuously updated with changes, reflecting the customer's requirements. People across the globe work on the same piece of software at the same time hence, there is a need for techniques that allow a smooth evolution of database as the design develops. Such methods utilize automated refactoring and continuous integration so that it supports agile methodologies for software development. These development techniques are applied on systems that are in pre-production stage as well on systems that have already been released. These techniques not only cover relevant changes in the database schema according to customer's changing needs, but also migration of modified data into the database and also customizing the database access code accordingly without changing the data semantics. History After using the waterfall model for a long time, the software industry has witnessed a rise ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Database Testing
Database testing usually consists of a layered process, including the user interface (UI) layer, the business layer, the data access layer and the database itself. The UI layer deals with the interface design of the database, while the business layer includes databases supporting business strategies. Purposes Databases, the collection of interconnected files on a server, storing information, may not deal with the same ''type'' of data, i.e. databases may be heterogeneous. As a result, many kinds of implementation and integration errors may occur in large database systems, which negatively affect the system's performance, reliability, consistency and security. Thus, it is important to test in order to obtain a database system which satisfies the ACID properties (Atomicity, Consistency, Isolation, and Durability) of a database management system. One of the most critical layers is the data access layer, which deals with databases directly during the communication process. Da ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Data Migration
Data migration is the process of selecting, preparing, extracting, and transforming data and permanently transferring it from one computer storage system to another. Additionally, the validation of migrated data for completeness and the decommissioning of legacy data storage are considered part of the entire data migration process. Data migration is a key consideration for any system implementation, upgrade, or consolidation, and it is typically performed in such a way as to be as automated as possible, freeing up human resources from tedious tasks. Data migration occurs for a variety of reasons, including server or storage equipment replacements, maintenance or upgrades, application migration, website consolidation, disaster recovery, and data center relocation. The standard phases , "nearly 40 percent of data migration projects were over time, over budget, or failed entirely." As such, to achieve an effective data migration, proper planning is critical. While the specifics of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Denormalization
Denormalization is a strategy used on a previously- normalized database to increase performance. In computing, denormalization is the process of trying to improve the read performance of a database, at the expense of losing some write performance, by adding redundant copies of data or by grouping data.S. K. Shin and G. L. SandersDenormalization strategies for data retrieval from data warehouses Decision Support Systems, 42(1):267-282, October 2006. It is often motivated by performance or scalability in relational database software needing to carry out very large numbers of read operations. Denormalization differs from the unnormalized form in that denormalization benefits can only be fully realized on a data model that is otherwise normalized. Implementation A normalized design will often "store" different but related pieces of information in separate logical tables (called relations). If these relations are stored physically as separate disk files, completing a database qu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Refactoring
In computer programming and software design, code refactoring is the process of restructuring existing computer code—changing the '' factoring''—without changing its external behavior. Refactoring is intended to improve the design, structure, and/or implementation of the software (its '' non-functional'' attributes), while preserving its functionality. Potential advantages of refactoring may include improved code readability and reduced complexity; these can improve the source codes maintainability and create a simpler, cleaner, or more expressive internal architecture or object model to improve extensibility. Another potential goal for refactoring is improved performance; software engineers face an ongoing challenge to write programs that perform faster or use less memory. Typically, refactoring applies a series of standardized basic ''micro-refactorings'', each of which is (usually) a tiny change in a computer program's source code that either preserves the behavior of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Test-driven Development
Test-driven development (TDD) is a software development process relying on software requirements being converted to test cases before software is fully developed, and tracking all software development by repeatedly testing the software against all test cases. This is as opposed to software being developed first and test cases created later. Software engineer Kent Beck, who is credited with having developed or "rediscovered" the technique, stated in 2003 that TDD encourages simple designs and inspires confidence. Test-driven development is related to the test-first programming concepts of extreme programming, begun in 1999, but more recently has created more general interest in its own right.Newkirk, JW and Vorontsov, AA. ''Test-Driven Development in Microsoft .NET'', Microsoft Press, 2004. Programmers also apply the concept to improving and debugging legacy code developed with older techniques.Feathers, M. Working Effectively with Legacy Code, Prentice Hall, 2004 Test-driven ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
