User Defined Function
A User Defined Function (English User Defined Function, abbreviation UDF) in a programming environment called a function that create the users themselves and can incorporate in their projects. It fulfills a task as a macro, but is implemented via a function call. UDFs are available in general programming languages such as Visual Objects, scripting languages such as PHP, special macro software as AutoIt and database languages such as SQL and Firebird.
The syntax of a UDF must be the syntax of the source language correspond with pre-defined standard functions and other UDFs can be used in the definition. As a UDF function must return exactly one return value.
Unlike a stored procedure can not be started as a UDF program.
Examples
The following UDF takes two date values , the function returns the younger date.
CREATE FUNCTION [ MaxDateValue ] ( v1 @ datetime, @ v2 datetime) RETURNS datetime AS BEGIN IF ( @ v1 <@ v2) RETURN ( @ v2) RETURN ( @ v1) END UDF after that is stored in the database, it can be used within a SQL query:
SELECT MaxDateValue ( the date of purchase order date ) FROM order External Table Function ("external table function " ) in SQL In this variant a ( unnamed ) SQL table is used for the return value exactly. You can within a SQL statement are wherever a SQL table can stand. On the SQL level, a control entry is defined that points to an external program. The database system typically supports several programming languages in which the program can be written.
- Programming
- Databases