Triggerele sunt o clasa speciala de proceduri stocate, asociate unei tabele, definite pentru a fi lansate in executie automat la initierea unei operatii de tip UPDATE, INSERT sau DELETE asupra tabelei in cauza.
Triggerele sunt un instrument puternic pentru implementarea a ceea ce in aplicatiile de baze de date poarta numele de business rules. Termenul se refera la acele reguli, constrangeri, ... Continuare
Proceduri stocate SQL
Procedurile stocate din SQL Server sunt similare procedurilor din alte limbaje de programare in sensul ca accepta parametrii de intrare, oferind valori prin parametrii de iesire catre aplicatiile apelante, continand instructiuni de programare care efectueaza operatii in baza de date, putand apela ale proceduri stocate.
La dezvolarea aplicatiilor( exemplu client/server) se poate vorbi despre ... Continuare
Intructiunea DELETE SQL
Folosita pentru stergerea tupleleor dintr-o tabela
DELETE [ FROM ] { nume_tabela | nume_vedere }
[ FROM { } [, ... n] ]
[ where {
| { [ CURRENT OF
{ { [ GLOBAL ] nume_cursor } | nume_variabila_cursor }
] }
}
... Continuare
Instructiunea UPDATE SDQL
Este folosita pentru a modifica date existente intr-o tabela.
UPDATE { nume_tabela | nume_vedere }
SET
{ nume_coloana = { expresie | DEFAULT | NULL }
| @variabila= expresie
| @variabila= coloana= expresie } [, … n]
[ FROM { } [, …n]
{ WHERE { < conditie_cautare >
| { ... Continuare
Instructiunea INSERT SQL
INSERT [INTO] [ nume_tabela | nume_vedere ]
{ [ (lista_coloane) ]
{ VALUES ( {DEFAULT | NULL | EXPRESIE } [ , ...n ] ) ]
| tabela_derivata
| instructiune_execute
}
}
| DEFAULT VALUES
Se foloseste pentru adaugarea de noi inregistrari in tabele existente pe un anumit ... Continuare
Instructiunea SELECT sql
SELECT [DISTINCT] nume_atribut1, nume_atribut2….``
[INTO tabela_noua]
FROM nume_relatie [variabila de tupla]…
WHERE conditie_de_cautare
[GROUP BY multime_atribut]
[HAVING conditie_de_cautare]
[ORDER BY multime_atribute [ ASC | DSC ] ]
Aceasta este operatia fundamentala in SQL si se mai ... Continuare
ADO .NET and Datasets
ADO.NET is a library of classes providing data access services and functionalities to the .NET programmer writing managed code. It provides consistent access to data sources such as Microsoft® SQL Server™, as well as other data sources exposed through OLE DB and XML; the supported operations fall into one of the three categories: retrieval, manipulation, or data updating.
The model of the ... Continuare
Database Objects with CLR Integration versus T-SQL
The latest .Net release of Visual Studio and SQL Server added a brand new feature, unique to the best of our knowledge: integration of the common language runtime (CLR) component of the .NET Framework for Microsoft Windows. What this means is that it is possible now to write stored procedures, triggers, user-defined types, user-defined functions (scalar and table-valued), and user-defined ... Continuare
Database Normalization
Normalization is the process that assures an efficient organization of data inside a database. The process is not very complicated but it can drastically improve the performance of a DBMS, especially in the case of a poor design. The two main goals of normalization are (1) to eliminate redundant data like what is happening when the same data is stored in more than one place, and (2) to ensure ... Continuare
Choosing the right key debate
DEFINITIONS
A surrogate key is a unique primary key generated by the RDMS that is not derived from any entity instance present in the database and whose only significance is to act as the primary key, definition adapted from [13].
An intelligent key is a type of key that contains embedded in it attributes of the entity, so data with actual significance. Some authors even use the term ... Continuare
Classifying Relationships
Relationships can be classified by their
• Degree - n-ary, unary, binary, ternary
• Connectivity - “one” or “many”
• Cardinality one-one, one-many, many-many
• Direction - parent, child
• Type - identifying, non-identifying
• Existence - mandatory, optional
Not all modeling methodologies use all these classifications.
The degree of a relationship is the number ... Continuare
Elements of ER model
ENTITIES
According to the English Dictionary [19], an entity is “Something that exists as a particular and discrete unit “, and adapted from [20] , a definition that can be the starting point in the discussion is that an entity is something that has a distinct, separate existence, though it need not be a material existence. In the context of databases, entities became the main discrete ... Continuare
Mobile Device World
Epocrates application will have two major releases, a desktop one and another one designed for mobile embedded devices. As proved so far, there are more possible architectures that can accommodate this goal. The most appropriate solution in this situation would be to integrate much of the logic of Epocrates into a database layer and leave the application objects to do what’s left of this job ... Continuare
Business Logic Issues
DEFINITION
Business logic refers to the business rules that are in fact the core business functionality services an application provides. A definition adapted after Shepker [13] can be :
Business logic, also called sometimes business rules, is the application code that drives using in following the processes that compose the business work. What is very important is that how and ... Continuare
SQL – The Structured Query Language
DEFINITION
Same as with databases or database models, there is an unanimous view about what SQL is and what its role and future is; the shortest definition to the best of our knowledge sounds like this : “SQL is a standardized query language for requesting information from a database “, adapted from Kauffman [11].
The first company to release a product based on a relational model was ... Continuare
Database History
Because most of the work in this project gravitates around relational data modeling, we start with the very beginning in this short history of the model, together with emphasizing its main aspects. Databases have existed from centuries as record keepings methods like ledgers or card catalogs and many others.
The foundations of the mathematical, scientific perspective on databases go as ... Continuare
Database Models
The application we are developing has to be thought of from the point of view of its main goal and function : it is a software package focused on storing and making available to users some data related to their field of activity : medicine. The other features can be ignored for the time being as they do not interfere with the discussion in this paragraph. It is obvious that the success of ... Continuare
Database Concepts and abstractions
DEFINITION
Many definitions of databases exist, out of which we summarize the one stated by Lelutiu [0] : a database is a stored data collection that has two main characteristics : (1) it provides data independence by means of a data scheme and its corresponding data definition language , and (2) it provides access to the stored data ( large volumes of it ) by means of its physical data ... Continuare
CSS
Fişierele CSS -Cascading Style Sheets- foi de stil în cascadă- utilizate la îmbunătăţirea prezentării unei pagini Web (adică a modului în care browserul o afişează). CSS vă permite să stabiliţi proprietăţi pentru elementele HTML utilizând o gamă uriaşă de valori. Având la dispoziţie mai mult de 100 de ... Continuare
Programare web pe partea de client folosind limbajul Java
Script
De ce avem nevoie pentru a rula scripturi concepute în limbajul JavaScript? Avem în primul rând nevoie de un browser care suporta JavaScript - de exemplu Netscape Navigator (începând cu versiunea 2.0) sau Microsoft Internet Explorer.
JavaScript este un limbaj de script, adică un limbaj de programare simplificat. Se numeşte JavaScript pentru că sintaxa acestui limbaj ... Continuare
