Creating a user-defined function

Learn how to create and configure external C/C++ user-defined functions (UDFs).

1. Declare the UDF to the server by using the CREATE FUNCTION or CREATE AGGREGATE FUNCTION statements. Write and execute these statements as commands, or use the appropriate CREATE statement using the Sybase Central New Function wizard.

   The external C/C++ form of the CREATE FUNCTION statement requires DBA or RESOURCE authority, so standard users do not have the authority to declare any UDFs of this type.

2. Write the UDF library identification function..
   
3. Define the UDF as a set of C or C++ functions. See Defining a scalar UDF or Defining an aggregate UDF.
4. Implement the function entry points in C/C++.
5. Compile the UDF functions and the library identification functions..
   
6. Link the compiled file into a dynamically linkable library.

• Creating a user-defined function using SQL Anywhere dialects
  Watcom-SQL and Transact-SQL are SQL dialects supported by SQL Anywhere, and can be used when creating user-defined functions.
• Declaring a scalar user-defined function in Sybase Central
  Sybase IQ supports simple scalar UDFs that can be used anywhere the SQRT function can be used. These scalar UDFs can be deterministic, which means that for a given set of argument values, the function always returns the same result value. Sybase IQ also supports nondeterministic scalar functions, which means that the same arguments can return different results.
• Declaring a user-defined aggregate function in Sybase Central
  Sybase IQ supports user-defined aggregate functions (UDAFs). The SUM function is an example of a built-in aggregate function. A simple aggregate function takes a set of argument values and produces a single result value from that set of inputs. User-defined aggregate functions can be written that can be used anywhere the SUM aggregate can be used.