The LANGUAGE PL/SQL
The SQL language is not United Nations programming language in the common sense of the word. It does not allow, for example, to define functions or factors, to perform iterations or conditional pointsers. This is not a defect in the origination of the language, but a deliberate direction of SQL to the operations of exquisite DE data in a large database, the priority being given to simplicity and efficiency. These two genus Termes have a strong implication in the context of a language of questioning, and journalist to precisely defined criteria (and constraints). The simplicity of a standard time language essentially relative to a baby declarative character, otherwise dowry to the ability to express DEs nut searches leaving the lupus system care to determine lupus best way to execute them. The standard time efficiency, on the other hand, defines normal features related to metropolis evaluation complexity that we will not extend here. Note however that the termination of a standard time SQL query always guaranteed, metallic element that is not lupus case of a program written in United Nations language additionally to powerful, .
It is therefore clear that SQL is not enough for the development of applications, and all relational SGBDs have, from the outset, proposed interfaces to associate it with in addition to traditional languages such as C or Java. These programming interfaces allow the use of SQL as a tool to recover data in programs performing a wide variety of tasks: graphical interfaces, bunch treatments, creation of compatibilities or web destinations, and so forth In a way, we can then consider SQL as an interface of access to the database, integrated into a general programming language. It is certainly child use in addition to current.
For some features, however, the use of an "external" programming language is inadequate or unsatisfactory. An evolution of the SGBD is therefore to propose, within the system, primitive programming that compensates for the relative lack of expressiveness of relational languages. This chapter describes these developments and their application to the creation of stored procedures and triggers. The first allow to enrich a database diagram by calculations or functions that cannot - sometimes even in very simple cases - be obtained with SQL; the latter extend the possibility of defining constraints.
Alongside these practical applications, the stored procedures simply illustrate the procedures for integrating SQL into a traditional programming language, and emphasize the limits of the use of a questioning language, and in addition to particularly the relational model.
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