存储过程英文

stored procedure

Stored procedureFrom Wikipedia, the free encyclopediaJump to: navigation, searchA stored procedure is a subroutine available to applications accessing a relational database system. Stored procedures (sometimes called a proc, sproc, StoPro, or SP) are actually stored in the database data dictionary.Typical uses for stored procedures include data validation (integrated into the database) or access control mechanisms. Furthermore, stored procedures are used to consolidate and centralize logic that was originally implemented in applications. Large or complex processing that might require the execution of several SQL statements is moved into stored procedures and all applications call the procedures only.Stored procedures are similar to user-defined functions (UDFs). The major difference is that UDFs can be used like any other expression within SQL statements, whereas stored procedures must be invoked using the CALL statement[citation needed]CALL procedure(…)orEXECUTE procedure(…)Stored procedures can 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 procedures may also contain declared variables for processing data and cursors that allow it to loop through multiple rows in a table. The standard Structured Query Language provides IF, WHILE, LOOP, REPEAT, CASE statements, and more. Stored procedures can receive variables, return results or modify variables and return them, depending on how and where the variable is declared.Contents [hide]1 Implementation2 Other uses3 Comparison with Dynamic SQL4 Difference between Stored Procedures and Functions5 Disadvantages6 References7 External links[edit] ImplementationThe exact and correct implementation of stored procedure varies from one database system to another. Most major database vendors support them in some form. Depending on the database system, stored procedures can be implemented in a variety of programming languages, for example SQL, Java, C, or C++. Stored procedures written in non-SQL programming languages may or may not execute SQL statements themselves.The increasing adoption of stored procedures led to the introduction of procedural elements to the SQL language in the SQL:1999 and SQL:2003 standards in the part SQL/PSM. That made SQL an imperative programming language. Most database systems offer proprietary and vendor-specific extensions, exceeding SQL/PSM. For example, Microsoft SQL Server allows for stored procedures to be written using Transact-SQL; Oracle calls its dialect PL/SQL, DB2 uses SQL/PL, PostgreSQL provides PL/pgSQL and also allows users to define their own function languages such as pl/perl or pl/php, and MySQL supports their own stored procedures that try to adhere closely to the SQL:2003 standard[edit] Other usesIn some systems, stored procedures can be used to control transaction management; in others, stored procedures run inside a transaction such that transactions are effectively transparent to them. Stored procedures can also be invoked from a database trigger or a condition handler. For example, a stored procedure may be triggered by an insert on a specific table, or update of a specific field in a table, and the code inside the stored procedure would be executed. Writing stored procedures as condition handlers also allow DBAs to track errors in the system with greater detail by using stored procedures to catch the errors and record some audit information in the database or an external resource like a file.[edit] Comparison with Dynamic SQLBecause stored procedure statements are stored directly in the database, this can remove the compilation overhead that is typically required in situations where software applications send inline (dynamic) SQL queries to a database. However, most database systems implement statement caches to avoid repetitive compilation of dynamic SQL statements. In addition, pre-compiled SQL statements, while avoiding some overhead, add to the complexity of creating an optimal execution plan because not all arguments of the SQL statement are supplied at compile time. Depending on the specific database implementation and configuration, mixed performance results will be seen from stored procedures versus generic queries or user defined functions.A major advantage with stored procedures is that they can run directly within the database engine. In a production system, this typically means that the procedures run entirely on a specialized database server, which has direct access to the data being accessed. The benefit here is that network communication costs can be avoided completely. This becomes particularly important for complex series of SQL statements.Stored procedures allow for business logic to be embedded as an API in the database, which can simplify data management and reduce the need to encode the logic elsewhere in client programs. This may result in a lesser likelihood of data becoming corrupted through the use of faulty client programs. Thus, the database system can ensure data integrity and consistency with the help of stored procedures.[edit] Difference between Stored Procedures and Functionsa. Only function can Return a value (to be precise using the Return keyword)b. Procedures can use ‘Return’ keyword but without any value being passedc. Functions could be used in select statements, provided they don’t do any data manipulation inside and also should not have any OUT, IN OUT parameters.d. Functions must return a value, but for procedure it is not compulsory.e. The Function can have only in parameter.[edit] DisadvantagesStored procedures are often said to be more secure than dynamic SQL, since users may have no direct table access. In real world, the database is most often used not by users, but by programmers. If they are restricted to a fixed set of procedures and not allowed to run proper queries, the system will perform poorly. In order to fix this, the developers need to have access to actually modify the procedures, which is far more administrative privilege than allowing simple select/insert/update/delete statements. Spurious changes to stored procedures may lead to destabilizing remote parts of code. Splitting project team into database and application developers creates extra bureaucracy barrier, which in non security-critical systems is mostly parasitic.Impossibility of using "where something in (value1, value2, ...)" may lead some developers to write code that passes SQL as a string to a stored procedure, leading to far more dangerous SQL injection attacks than are feasible with sanitized parameterised queries.Further more, some modern DBMS systems (notably from MS SQL Server 2000 onwards) don't offer any performance benefits of using stored procedures - they are compiled and cached in the same manner as dynamic SQL is. Indeed, it has been observed that using simple CRUD procedures creates only an extra efficiency overhead.[edit] ReferencesThis article does not cite any references or sources. Please help improve this article by adding citations to reliable sources. Unverifiable material may be challenged and removed. (October 2007)

描绘被一仁把行动带到上下文-开关在中间过程.答案:一般地说,操作系统必须去除了现时跑步的状态以外加工和交还计划被下一步运作过程的状态.典型保留一过程的状态包含计算机中央处理器登记的除了记忆分配价值观在所有当中.上下文转辙器必须也动很多特定建筑 -的包含使数据和指令秘窖变红手术

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复数（plural，等于pl）

1、function是SQL的函数 是由一个或多个 Transact-SQL 语句组成的子程序，可用于封装代码以便重新使用。Microsoft® SQL Server™ 并不将用户限制在定义为 Transact-SQL 语言一部分的内置函数上，而是允许用户创建自己的用户定义函数。 可使用 CREATE FUNCTION 语句创建、使用 ALTER FUNCTION 语句修改、以及使用 DROP FUNCTION 语句除去用户定义函数。每个完全合法的用户定义函数名 (database_name.owner_name.function_name) 必须唯一。 必须被授予 CREATE FUNCTION 权限才能创建、修改或除去用户定义函数。不是所有者的用户在 Transact-SQL 语句中使用某个函数之前，必须先给此用户授予该函数的适当权限。若要创建或更改在 CHECK 约束、DEFAULT 子句或计算列定义中引用用户定义函数的表，还必须具有函数的 REFERENCES 权限。 在函数中，区别处理导致删除语句并且继续在诸如触发器或存储过程等模式中的下一语句的 Transact-SQL 错误。在函数中，上述错误会导致停止执行函数。接下来该操作导致停止唤醒调用该函数的语句。 用户定义函数的类型2、Procedure是SQL的存储过程 存储过程是由流控制和SQL语句书写的过程，这个过程经编译和优化后存储在数据库服务器中，应用程序使用时只要调用即可。在ORACLE中，若干个有联系的过程可以组合在一起构成程序包。 存储过程是利用SQL Server所提供的Transact-SQL语言所编写的程序。Transact-SQL语言是SQL Server提供专为设计数据库应用程序的语言，它是应用程序和SQL Server数据库间的主要程序式设计界面。它好比Oracle数据库系统中的PL-SQL和 Informix的数据库系统结构中的Informix- 4GL语言。这类语言主要提供以下功能，让用户可以设计出符合引用需求的程序： 1)、变量说明 2)、ANSI兼容的SQL命令(如Select,Update….) 3)、一般流程控制命令(if…else…、while….) 4)、内部函数

计算机数据库中的“存储过程”Stored procedure in a computer database"计算机数据库中的“存储过程”Stored procedure in a computer database"

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